ST AN3301 Application note

AN3301

Application note

S-Touch® STMPE812A: a hardware and software guide

Introduction

The STMPE812A is a 4-wire resistive touchscreen controller with an integrated 4-bit port expander. The touchscreen controller is designed to be fully autonomous, requiring only minimal CPU intervention for sampling, filtering and preprocessing operations.

The purpose of this document is to highlight the guidelines and information complementary to the datasheet that is necessary for a proper operation of the STMPE812A device in applications.

The first part of the document highlights information on the hardware. This includes external components/connectivity, power, PCB design and etc.

The second part of the document focuses on information in software in which programming reference codes are shown. This part is to be used in conjunction with the STMPE812A software library available in www.st.com.

December 2010 Doc ID 18161 Rev 1 1/35

www.st.com

Contents AN3301

Contents

1 Hardware . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5

1.1 Typical application circuit and external components . . . . . . . . . . . . . . . . . 5

1.2 Power supply . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6

1.2.1 Power sequence (fail safe) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6

1.3 Power modes transition . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7

1.4 Touchscreen tracks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8

1.4.1 Track resistance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8

1.5 Noise prevention . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9

1.6 Noise filtering . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9

1.7 PWM controller . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10

1.8 ADC controller . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11

1.9 GPIO output configurations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11

1.9.1 Push-pull . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11

1.9.2 Open drain . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12

2 Software . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13

2.1 Touchscreen controller acquisition modes . . . . . . . . . . . . . . . . . . . . . . . . 13

2.1.1 Data acquisition by internal timer (ACQ_mode “00”) . . . . . . . . . . . . . . . 13

2.1.2 Data acquisition by ACQ command (ACQ_mode “01”) . . . . . . . . . . . . . 14

2.1.3 Data acquisition by host read control (ACQ_mode “10”) . . . . . . . . . . . . 14

2.2 Embedded data valid bit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16

2.3 Pen down interrupt mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16

2.4 TSC_DATA read . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17

2.5 Touchscreen controller sampling . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17

2.6 Programming guide . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19

2.6.1 Touchscreen initialization and interrupt handling (pen down mode) . . . 19

2.6.2 Touchscreen initialization and interrupt handling (normal interrupt mode) 23

2.6.3 GPIO initialization and interrupt handling . . . . . . . . . . . . . . . . . . . . . . . 28

2.6.4 ADC initialization and interrupt handling . . . . . . . . . . . . . . . . . . . . . . . . 29

2.6.5 PWM initialization and interrupt handling . . . . . . . . . . . . . . . . . . . . . . . 32

3 Revision history . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34

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AN3301 List of figures

List of figures

Figure 1. Typical application schematic . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5

Figure 2. Track resistance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8

Figure 3. Noise prevention . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9

Figure 4. PWM LED driving configurations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10

Figure 5. GPIO push-pull configuration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11

Figure 6. GPIO open drain configuration (output low) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12

Figure 7. GPIO open drain configuration (output high) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12

Figure 8. Data acquisition by internal timer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13

Figure 9. Data acquisition by ACQ command . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14

Figure 10. Data acquisition by host read command. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15

Figure 11. TSC data register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16

Figure 12. Touchscreen controller sampling . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17

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List of tables AN3301

List of tables

Table 1. Power modes vs. touchscreen/GPIO/Interrupt/PWM data . . . . . . . . . . . . . . . . . . . . . . . . . . 7

Table 2. Example of sampling time calculation. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18

Table 3. Document revision history . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34

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AN3301 Hardware

1 Hardware

1.1 Typical application circuit and external components

Figure 1. Typical application schematic

1.65V – 3.6V

Y+

VCC

SDA

SCL

INT

RESET

VCC

RESETN

INT (P 2)

SCLK

SDATA

STMPE812A

X+

Y-

X-

(P1)ADC

(P0)ADDR

GND

4-wire

resistive

touchscreen

ADC input

Note: 1 P0 pin is the I

2 P1 pin is configurable to GPIO/ADC/PWM (ADC Vin must be less than V

3 P2 pin is configurable to GPIO/INT

4 Assuming GPIO controlling RESET input is of open drain type

In a typical application, the following external components are required:

● R1: 2.2k-10kΩ pull up resistor at RESET

● R2: 2.2k-10kΩ pull up resistor at INT.

● R3: 2.2k-10kΩ pull up resistor at SCLK

● R4: 2.2k-10kΩ pull up resistor at SDATA

● R5: 2.2k-10kΩ pull up resistor at ADDR

● C1: 100 nF capacitor at V

C address bit upon power up or reset and is configurable to GPIO

)

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Hardware AN3301

1.2 Power supply

The implementation and layout of the power connection’s section is fundamental for the correct operation of the STMPE812A touchscreen controller.

The STMPE812A device is equipped with a 12-bit ADC that is used during the touchscreen controller and auxiliary voltage measurement operations.

The analog blocks require a clean and stable supply voltage in order to operate in optimum performance. In the STMPE812, the analog blocks and the digital core are supplied by V The operating V with the increase in V

voltage range is 1.65 V to 3.6 V. Power consumption will be increased

. The lowest power consumption is at VCC = 1.8 V.

It is a good practice to connect a 0.1 pin.

1.2.1 Power sequence (fail safe)

All GPIOs and sense pins of STMPE812A are NOT fail safe. This means that it is necessary to make sure that the V inputs.

All other pins (SCL and SDA) are with fail safe structure. It is possible to turn on the pull-up supply before V

supply to STMPE812A is first turned before driving the GPIO

µF filtering capacitor as close as possible to the V

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AN3301 Hardware

1.3 Power modes transition

The following table highlights the states of touchscreen FIFO, GPIO, Interrupt and PWM during the various power modes:

– Active mode

– Hibernation mode

– Reset

Table 1. Power modes vs. touchscreen/GPIO/Interrupt/PWM data

Description Active mode Hibernation mode

Touchscreen FIFO data Active Sustained Cleared

GPIO configuration, pin state and data

Interrupt configuration and data

PWM configuration and data

Active Sustained Cleared

Reset (HW, SW, POR

and General call)

Hibernation mode is entered automatically when ALL of the following listed activities are met:

● Absent of I

● PWM disabled

● ADC disabled

● Absent of GPIO input transition for 10 ms

● Absent of touchsceen or pen down interrupt for 10 ms

C transaction with valid STMPE812A slave address for 10 ms

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1.4 Touchscreen tracks

The touchscreen tracks (X+, X-, Y+, Y-) are sensitive lines. Noise may be captured by the touchscreen tracks if the line is too long and if placed nearby noisy lines, for example the digital data lines and the I2C/SPI lines.

Although there is no recommended standard for track sizes, tracks that are too long reduce the resolution of the touchscreen controller. As a matter of fact, long tracks introduce a voltage drop during the measurement cycle at the terminal of the touchscreen panel.

1.4.1 Track resistance

Any track has a certain amount of resistance, thus reducing the effective resolution of the touchscreen controller.

During the measurement, the current flows to the touchscreen panel through the tracks. If the resistance is too high, the voltage in the panel terminal is no longer at the same level as VIO and GND.

From Figure 2 it can be seen that, during the measurement cycle, the device bias the touchscreen panel with the VIO voltage. Due to the track resistance, the voltage at panel's terminals is:

Equation 1

Vx V

R1 R2 Rx++()⁄⋅=

Hence, the effective resolution is reduced by the same factor as well. The track resistance may be reduced by designing the track as short as possible with a reasonable width.

Figure 2. Track resistance

Tr ack resistance, R1

VIO

To uch panel

Tr ack resistance, R2

GND

resistance, Rx

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AN3301 Hardware

1.5 Noise prevention

Noise may be coupled to the tracks connecting the touchscreen and this should be prevented as much as possible.

Two practices may be applied:

1. Prevent the tracks overlap with other noisy signal tracks, such as I2C/SPI lines and digital data lines. If the overlap is not avoidable, GND lines separation between touchscreen lines and noisy lines is recommended (in more than 2 layers PCB).

2. Put GND shielding at each side of touchscreen tracks routing.

Figure 3. Noise prevention

TSC

TSC tracks

Top Layer

1.6 Noise filtering

A filtering capacitor can be placed on the touchscreen tracks to further suppress the noise. In this case, the best location for the filtering capacitor is as near as possible to the STMPE812A sense pins (X+, X-, Y+, Y-).

The values recommended for the filtering capacitor are:

1. 1-2 nF for an LCD less than 6 inches

2. 5-10 nF for an LCD bigger than 6 inches

Noisy tracks

Bottom Layer

GNDGND

GND

Oth er

Noisy lin e

AM004194V2

The Settling time and Touch detect delay registers must be set correctly to adapt to the filtering capacitor, otherwise the touchscreen controller may not work properly. Additional information is found in the STMPE812A datasheet.

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Hardware AN3301

1.7 PWM controller

The STMPE812A is integrated with push-pull type of GPIO/PWM outputs. At VCC of 3.3 V, the outputs are able to provide 8mA of sourcing (out of device) and 12mA of sinking (into device) current capability. As such, STMPE812A is able to support LED driving in both sourcing and sinking configuration.

Note: the PWM timing and duty cycle settings in datasheet are based on a LED sourcing configuration. When used in sinking configuration, the inversion must be executed accordingly.

Figure 4. PWM LED driving configurations

C u rrent s o urcing

configu ra tion (8 mA)

S TMPE8 12A

PWM(A1)

C u rrent s inking

configu ra tion (12mA)

S TMPE8 12A

PWM(A1)

VCC

AM004194V1

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AN3301 Hardware

1.8 ADC controller

The STMPE812A is equipped with a 12-bit analog-to-digital converter (ADC). Besides the use for ADC conversion during touchsceen controller operation, it is possible to be used as general purpose ADC conversion for up to maximum two external auxiliary analog signals feed through pins B2 and C2.

The touchscreen controller has the priority for the ADC conversion. Selection of conversion of the two external auxiliary analog signals is programmed through Bit[0] of the ADC control register (0x20).

Whenever the touchscreen data acquisition is initiated, the ADC conversion is triggered automatically without needs to program the ADC control register. Writing ‘1’ to Bit[6] of ADC Control register to initialize conversion for Touchscreen data is redundant and will result in higher current consumption if ADC is in continuous capture mode.

The STMPE812A is integrated with an internal charge pump in order to ensure ADC performance in low V ADC control register in the device initialization phase whenever the V

Important: If V

disabled to prevent possible reliability issue or permanent damage of the device.

condition. The internal charge pump should be turned on through

is less than 2.5 V.

is higher than 2.5 V, it is important to ensure the charge pump is

1.9 GPIO output configurations

The STMPE812A provides push-pull type of GPIO output. If open drain GPIO outputs are required, it is configurable, with a tweak to the software programming routine. See Figure 5,

Figure 6 and Figure 7.

1.9.1 Push-pull

Set the GPIO to output state through PORT_FUNTION (0x04) register. Input path will be disabled. Output path will be enabled in push-pull configuration.

Figure 5. GPIO push-pull configuration

OUTPUT

INPUT

STMPE812A

disabled

enabled

GPIOxGPIOx

AM004195V1

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Hardware AN3301

1.9.2 Open drain

GPIO output driven low by STMPE812A

Set the GPIO to output state through PORT_FUNTION (0x04) register. Input path is disabled. Set the output state to LOW through GPIO_CLR_PIN (0x11) register. Output path is enabled and pull GPIO pin LOW.

Figure 6. GPIO open drain configuration (output low)

STMPE812A

enable

OUTPUT

GPIOx

INPUT

disable

VCC

External pull up

GPIOx

GPIO = LOW

AM004197V1

GPIO output pulled high by external pull up resistor

Set the GPIO to input state through PORT_FUNTION (0x04) register. Input path is enabled and output path disabled. GPIO will be pulled high by external pull up resistor.

Figure 7. GPIO open drain configuration (output high)

STMPE812A

VCC

enable

OUTPUT

INPUT

disable

12/35 Doc ID 18161 Rev 1

GPIOx

GPIO = HIGH

External pull up

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AN3301 Software

2 Software

2.1 Touchscreen controller acquisition modes

2.1.1 Data acquisition by internal timer (ACQ_mode “00”)

In this mode, the system configures STMPE812A to sample at a predefined rate (e.g. 10ms) through TSC_Sampling_Rate register (0x43). On detecting a touch, it starts the sensing sequence and on completion of sampling (thus data available for reading), it interrupts the Host. If the Host does not access the data by the time the next data is available, the old data is overwritten.

Programming sequence:

1. Initialize touchscreen controller

2. Initialize interrupt

3. Wait for interrupt

4. Upon interrupt, read ISR

5. Upon touch data available, read touch data

Figure 8. Data acquisition by internal timer

Initialization No Touch Touched No Touch

Initializ ation

Agenda:

STMPE812A sens interrupt to Host

Host read ISR

Host read touch data when available

No Touch

Sampling

Touched

Sampling

AM004199V1

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Software AN3301

2.1.2 Data acquisition by ACQ command (ACQ_mode “01”)

In this acquisition mode, the STMPE812A merely informs the system host on detecting a touch. As and when sampling is desired, host issues an “ACQ” command that sets STMPE812A into a complete sampling cycle. Host may read the data after a period of time, or poll the interrupt status bit for data availability.

Programming sequence:

1. Initialize touchscreen controller

2. Initialize interrupt (Pen Down mode)

3. Wait for interrupt

4. Upon interrupt, issue ACQ command

5. Poll ACQ bit for data available

6. Upon touch data available, read touch data

Figure 9. Data acquisition by ACQ command

Initialization No Touch Touched No Touch

Initializ ation

Agenda:

STMPE812A sens touched interrupt to Host

Host issues ACQ command

Host polls ACQ bit or ISR for sampling completion

Host read touch data when available

No Touch

Sampling

Touched

Sampling

2.1.3 Data acquisition by host read control (ACQ_mode “10”)

The data acquisition by the host read control is the most bandwidth efficient method for touchscreen interfaces. For 100 Hz sampling with 12-bit X, 12-bit Y, 8-bit Z, only one I transaction (5 bytes data read) is required for every 10 ms. Inclusive of overheads, this translates to approximately 100 bit time.

At 400 kHz I

A new sample is taken every time the host reads the previously sampled data. If host reads the data late, the device simply stays longer in hibernation.

C speed, this is just 2.5% of total bandwidth.

AM004200V1

Note: It is necessary to counter check with the data valid bit for each data read.

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AN3301 Software

Programming sequence:

1. Initialize touchscreen controller

2. Initialize interrupt (pen down mode)

3. Wait for interrupt

4. Upon interrupt, issue data read (counter check with the embedded data valid bit for the validity of the corresponding data)

5. Start host timer (typical 10ms depends on the programmed sampling time)

6. Upon time out, issue data read (counter check with the embedded data valid bit for the validity of the corresponding data)

Figure 10. Data acquisition by host read command

Touched

Initialization

No Touch No Touch

Sampling

Touched

Sampling

Agenda:

STMPE812 sends touched interrupt to Host

Host read touch data

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Software AN3301

2.2 Embedded data valid bit

In order to facilitate a more bandwidth efficient for data read, it is possible to program through Bit[5] of TSC_DET_CFG2 register (0x42) whereby the data valid bit is embedded in within the first byte of the touch data (FIFO).

Figure 11. TSC data register

TSC_DET_CFG2 Register

Bit[4]

OpMode

Bit[5]

StatusRead

Number of

bytes to

read from

TSC_Data

510

411

[11:4] of X400

[11:4] of X301

Da ta valid

status

Da ta valid

status

[3:0] of X

[11:8] of Y

[3:0] of X

[11:8] of Y

[11:4] of X

[3:0] of X

[11:8] of Y

[3:0] of X

[11:8] of Y

[7:0] of Y

RSVDVALIDRSVD

01234567

Byte4Byte3Byte2Byte1Byte0

-[7:0] o f Z[7:0] of Y

--[7:0] of Y

[7:0] of Z[7:0] of Y



AM08680V1

In applications whereby no GPIO input/PWM/ADC is used and Pen Down interrupt mode is selected, it is no longer necessary to read the ISR register. The data valid info can be obtained through the embedded data valid bit and the touch release info can be obtained merely by observing the INT pin signal. (ie. INT low: touched; INT high: release).

2.3 Pen down interrupt mode

In Pen down interrupt mode, the INT pin signal is an OR function of the Pen Down and other enabled GPIO/PWM/ADC interrupts at Port 0 to Port 3.

It is recommended to use Pen Down mode when the GPIO/PWM/ADC functions are not required or the GPIO/PWM/ADC interrupts are not enabled. In this condition, the INT signal provides the exclusive indication for touched (INT low) and release (INT high).

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AN3301 Software

2.4 TSC_DATA read

The TSC_DATA contains the converted data for touchscreen controller. Three to five bytes readings are required depending on the programmed value in TSC_DET_CFG2 register.

In order to preserve the integrity of the data, it is mandatory to ensure the following:

– System host to read exactly the number of bytes according to the programmed

operating mode

–I

C host to insert a STOP condition after each data read command

2.5 Touchscreen controller sampling

The touchscreen controller sampling time is determined by the following programmable parameters:

– Touch detect delay

– Settling time

– ADC conversion time

– MAV (median average filter)

– TSC operating mode (X/Y or X/Y/Z acquisition)

Figure 12 illustrates the diagram of a complete sampling cycle. MAV is acting within the

Sampling period of X, Y and Z respectively.

Figure 12. Touchscreen controller sampling

-

Settling Time

To uch Detect Delay

Sampling X

A complete sampling cycle

Settling Time

Sampling Y

Settling Time

Sampling Z

To uch Detect Delay

AM08681V2

The overall sampling time/frequency can be calculated with below formulae.

Sampling time in X/Y/Z mode = touch detect delay *2 + (settling time + (ADC conversion time * MAV)) * 3

Time taken for sampling in X/Y/Z mode = touch detect delay *2 + (settling time + (ADC conversion time * MAV)) * 2

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Software AN3301

Table 2. Example of sampling time calculation

Sampling

ADC

conversion time

50 µs

Touch detect

delay

Settling time MAV

40 µs 40 µs None

50 µs 40 µs 40 µs 10-2

50 µs 640 µs 640 µs 20-4

time/freq

(complete X/Y/Z

sample sets)

40*2 +

3*(40+(50*1))

=350 µs (2.8 K

sample sets/sec)

40*2 + 3*(40+

(50*10))

=1700 µs (588

sample sets/sec)

640*2 + 3*(640+

(50*20))

=6200 µs (161

sample sets/sec)

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2.6 Programming guide

In this section, the reference software programming code is shared based on the general application of the STMPE812A. This includes the initialization and interrupt handling routines for touchscreen controller (in all 3 acquisition modes and both normal and pen down interrupt modes), GPIO, ADC and PWM.

The reference code is supplemented by the STMPE812A software library.

2.6.1 Touchscreen initialization and interrupt handling (pen down mode)

The following is an example for touchscreen initialization, interrupt servicing routine in pen down mode, whereby all other interrupt sources (eg. GPIO, PWM and ADC) are not used in the application.

A: Initialization

void STMPE812A_Initialization (void) {

/*Enabling the Soft Reset in the System Control Register (0x03)*/ STMPE812A_SoftReset ();

/*Enabling the ADC and TSC Clocks in the System Control Register (0x03)*/ STMPE812A_SetClock (STMPE812A_ENABLE, STMPE812A_ADC_CLK|STMPE812A_TSC_CLK);

/*Setting the Port - 2 as a special function in the Port Function Control Register (0x04)*/ STMPE812A_SetPortFunction (STMPE812A_PORT2, STMPE812A_PORT_FUNC_SPECIAL_FUNC);

/*Setting the MAV_MODE [2:0] as ‘20 remove 4’, Precharge [1:0] as ‘no pre-charge’ and Current _Limit [1:0] as ‘20mA’ in the TSC Control Register (0x40) respectively*/ STMPE812A_SetTSCController (STMPE812A_TSC_MAV_20_4, STMPE812A_TSC_NO_PRE, STMPE812A_TSC_Current20M);

/*Setting the PenStrength [1:0] as ‘Most Sensitive (20K Pull-Up)’, TDetDly [2:0] as ‘40us’ and Settling [2:0] as ‘40us’ in the TSC Detection Configuration 1 Register (0x41) respectively*/ STMPE812A_ConfigureTSC (STMPE812A_TSC_MOST_SEN, STMPE812A_TSC_TDD40, STMPE812A_TSC_PDST40);

/*Setting the TSC operating mode OpMode [4] as ’12-bit X, 12-bit Y, 8-bit Z acquisition’ in the TSC Detection Configuration 2 Register (0x42)*/ STMPE812A_SetTSCOpMode (STMPE812A_DISABLE);

/*Enabling the StatusRead [5] in the TSC Detection Configuration 2 Register (0x42)*/ STMPE812A_SetTSCStatusRead (STMPE812A_ENABLE);

/*Setting the Acq_Mode [7:6] as ‘Data acquisition timed by internal timer’ in the TSC Detection Configuration 2 Register (0x42)*/ STMPE812A_SetTSCAcquisitionMode (STMPE812A_TSC_INTERNAL_TIMER); /*Setting the Acq_Mode [7:6] as ‘Data acquisition triggered by a write to “ACQ” bit’ in the TSC Detection Configuration 2 Register (0x42)*/ //STMPE812A_SetTSCAcquisitionMode (STMPE812A_TSC_TRI_ACQ); /*Setting the Acq_Mode [7:6] as ‘Data acquisition using Host-Controlled Sampling Rate Control’ in the TSC Detection Configuration 2 Register (0x42)*/ //STMPE812A_SetTSCAcquisitionMode (STMPE812A_TSC_HC_SRC);

/*Setting the TSC sampling rate value of ‘0x0A’ in the TSC Sampling Rate Register (0x43)*/ STMPE812A_SetTSCSamplingRate (0x0A);

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Software AN3301

/*Setting the INT_Mode [7] as ‘Pendown Interrupt Mode’ in the Interrupt Control Register (0x08)*/ STMPE812A_SetInterruptMode(STMPE812A_INT_MODE_PEN_DOWN);

/*Enabling the Global Interrupt in the Interrupt Control Register (0x08)*/ STMPE812A_EnableGlobalInterrupt (TRUE);

/*Enabling the interrupt from the system related source of TSC_TOUCH and TSC_DATA to the host in the Interrupt Enable Register (0x09)*/ STMPE812A_EnableInterrupt (STMPE812A_INT_TSC_TOUCH|STMPE812A_INT_TSC_DATA, TRUE);

/*Enabling the TSC operation in the System Control Register (0x03)*/ STMPE812A_EnableTouchscreen (TRUE);}

B: Interrupt handling (pen down mode)

Data acquisition timed by internal timer

void IRQHandler (void) {

u8 data [5];

if (GetITStatus (INTERRUPT_LINE)! = RESET) { /*Clearing the Interrupt pending bit from the Micro-controller*/ ClearITPendingBit (INTERRUPT_LINE);

/*Checking the Interrupt Pin Status goes low*/ if ((GPIO_INTERRUPT->IDR & GPIO_PIN_INTERRUPT) == 0) { /*Start host timer with an interval of 13ms*/ /*Check below for the timer routine*/

TIM_Cmd (TIM2, ENABLE); } } }

Data acquisition triggered by a write to “ACQ” bit

void IRQHandler (void) {

u8 data [5];

if (GetITStatus (INTERRUPT_LINE)! = RESET) { /*Clearing the Interrupt pending bit from the Micro-controller*/ ClearITPendingBit (INTERRUPT_LINE);

/*Checking the Interrupt Pin Status goes low*/ if ((GPIO_INTERRUPT->IDR & GPIO_PIN_INTERRUPT) == 0) { /*Start host timer with an interval of 0ms*/

/*Check below for the timer routine*/

TIM_Cmd (TIM2, ENABLE); } } }

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Data acquisition using host-controlled sampling rate control

void IRQHandler (void) {

u8 data [5];

if (GetITStatus (INTERRUPT_LINE)! = RESET)

{

/*Clearing the Interrupt pending bit from the Micro-controller*/

ClearITPendingBit (INTERRUPT_LINE);

/*Checking the Interrupt Pin Status goes low*/

if ((GPIO_INTERRUPT->IDR & GPIO_PIN_INTERRUPT) == 0)

{

/*Reading the Interrupt status register and Dummy data of 4 bytes of x, y & z data from the register address of 0x44 to 0x48*/

I2C_Read_Data (STMPE812A_SLAVE_ADDR, STMPE812A_TSC_DATA, 5, &data [0]);

/*Start host timer with an interval of 13ms*/

/*Check below for the timer routine*/

TIM_Cmd (TIM2, ENABLE);

}

Micro-controller timer routine

Data acquisition timed by internal timer or data acquisition using host-controlled sampling rate control:

void TIM2_IRQHandler (void) {

if (TIM_GetITStatus (TIM2, TIM_IT_CC1) != RESET)

{

/*Clearing the Timer 2 Interrupt pending bit from the Micro-controller*/

TIM_ClearITPendingBit (TIM2, TIM_IT_CC1);

/*Reading the Interrupt status register and 4 bytes of x, y & z data from the register address of 0x44 to 0x48*/

I2C_Read_Data (STMPE812A_SLAVE_ADDR, STMPE812A_TSC_DATA, 5, &Touch_Data [0]);

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/*Sets the global variable (Is_Pen_Down) to handle the global variables (Touch_Data [1] to Touch_Data [4] i.e. 4 bytes of x, y & z data coordinates) in the main while loop*/

Is_Pen_Down = TRUE;

/*Handling Coordinates codes should be here */

/*Checking either the bit 0 or 1 or both (touch bit [or] data bit [or] touch and data bits) value from Interrupt status register goes high*/

if ((Touch_Data [0] & 0x03) > 0)

{

/*Getting the Captured value from the Micro-controller Timer2 CNT register*/

Capture = TIM2->CNT;

/*Setting the (Captured value+CCR1_VAL) to the Micro-controller Timer2 CCR1 register.*/

TIM_SetCompare1 (TIM2, capture + CCR1_Val);

/*Enabling the Micro-controller Timer2 for 13ms*/

TIM_Cmd (TIM2, ENABLE);

}

else

{

/*Disabling the Micro-controller Timer2*/

TIM_Cmd (TIM2, DISABLE);

/*Resets the global variable (Is_Pen_Down) to clear the point (x, y & z data coordinates) in the main while loop*/

Is_Pen_Down = FALSE;

}

}}

Data acquisition triggered by a write to “ACQ” bit

void TIM2_IRQHandler (void) {

if (TIM_GetITStatus (TIM2, TIM_IT_CC1) != RESET) {

/*Clearing the Timer 2 Interrupt pending bit from the Micro-controller*/

TIM_ClearITPendingBit (TIM2, TIM_IT_CC1);

/* Sets the ACQ [4] in the TSC Control Register (0x40) */ STMPE812A_InitiateAcquisition ();

/* Waiting until the ACQ [4] in the TSC Control Register (0x40) goes low */ while (!STMPE812A_IsAcquisitionComplete ())

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{}

/*Reading the Interrupt status register and 4 bytes of x, y & z data from the register address of 0x44 to 0x48*/ I2C_Read_Data (STMPE812A_SLAVE_ADDR, STMPE812A_TSC_DATA, 5, &Touch_Data [0]);

/*Sets the global variable (Is_Pen_Down) to handle the global variables (Touch_Data [1] to Touch_Data [4] i.e. 4 bytes of x, y & z data coordinates)*/ Is_Pen_Down = TRUE;

/*Handling Coordinates codes should be here */

/*Checking either the bit 0 or 1 or both (touch bit [or] data bit [or] touch and data bits) value from Interrupt status register goes high*/ if ((Touch_Data [0] & 0x03) > 0) { /*Getting the Captured value from the Micro-controller Timer2 CNT register*/ Capture = TIM2->CNT;

/*Setting the (Captured value+CCR1_VAL) to the Micro-controller Timer2 CCR1 register.*/ TIM_SetCompare1 (TIM2, capture + CCR1_Val);

/*Enabling the Micro-controller Timer2 for 0ms*/ TIM_Cmd (TIM2, ENABLE); } else { /*Disabling the Micro-controller Timer2*/ TIM_Cmd (TIM2, DISABLE);

/*Resets the global variable (Is_Pen_Down) to clear the point (x, y & z data coordinates) in the main while loop*/ Is_Pen_Down = FALSE; } }}

2.6.2 Touchscreen initialization and interrupt handling (normal interrupt mode)

The following is an example for device initialization, interrupt servicing routine in normal interrupt mode.

A: Initialization

void STMPE812A_Initialization (void) {

/*Enabling the Soft Reset in the System Control Register (0x03)*/ STMPE812A_SoftReset ();

/*Enabling the ADC and TSC Clocks in the System Control Register (0x03)*/ STMPE812A_SetClock (STMPE812A_ENABLE, STMPE812A_ADC_CLK|STMPE812A_TSC_CLK);

/*Setting the Port - 2 as a special function in the Port Function Control Register (0x04)*/ STMPE812A_SetPortFunction (STMPE812A_PORT2, STMPE812A_PORT_FUNC_SPECIAL_FUNC);

/*Setting the MAV_MODE [2:0] as ‘20 remove 4’, Precharge [1:0] as ‘no pre-charge’ and Current _Limit [1:0] as ‘20mA’ in the TSC Control Register (0x40) respectively*/

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STMPE812A_SetTSCController (STMPE812A_TSC_MAV_20_4, STMPE812A_TSC_NO_PRE, STMPE812A_TSC_Current20M);

/*Setting the TSC operating mode OpMode [4] as ’12-bit X, 12-bit Y, 8-bit Z acquisition’ in the TSC Detection Configuration 2 Register (0x42)*/ STMPE812A_SetTSCOpMode (STMPE812A_DISABLE);

/*Disabling the StatusRead [5] in the TSC Detection Configuration 2 Register (0x42)*/ STMPE812A_SetTSCStatusRead (STMPE812A_DISABLE);

/*Setting the TSC sampling rate value of ‘0x0A’ in the TSC Sampling Rate Register (0x43)*/ STMPE812A_SetTSCSamplingRate (0x0A);

/*Setting the INT_Mode [7] as ‘Normal Interrupt Mode’ in the Interrupt Control Register (0x08)*/ STMPE812A_SetInterruptMode(STMPE812A_INT_MODE_NORMAL);

/*Setting the INT_Type [1] as ‘Edge Interrupt Type’ in the Interrupt Control Register (0x08)*/ STMPE812A_SetInterruptType (STMPE812A_INT_TYPE_EDGE);

/*Enabling the Global Interrupt in the Interrupt Control Register (0x08)*/

STMPE812A_EnableGlobalInterrupt (TRUE);

/*Enabling the interrupt from the system related source of TSC_DATA and TSC_RELEASE to the host in the Interrupt Enable Register (0x09)*/

/*For Acq_Mode [7:6] in the TSC Detection Configuration 2 Register (0x42) is set as ‘Data acquisition timed by internal timer’*/

STMPE812A_EnableInterrupt (STMPE812A_INT_TSC_DATA|STMPE812A_INT_TSC_REL, TRUE);

/*Enabling the interrupt from the system related source of TSC_TOUCH, TSC_DATA and TSC_RELEASE to the host in the Interrupt Enable Register (0x09)*/

/*For Acq_Mode [7:6] in the TSC Detection Configuration 2 Register (0x42) is set as either ‘Data acquisition triggered by a write to “ACQ” bit’ (OR) ‘Data acquisition using Host-Controlled Sampling Rate Control’*/

//STMPE812A_EnableInterrupt (STMPE812A_INT_TSC_TOUCH|STMPE812A_INT_TSC_DATA|STMPE812A_INT_TSC_REL, TRUE);

/*Enabling the TSC operation in the System Control Register (0x03)*/

STMPE812A_EnableTouchscreen (TRUE);}

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B: Interrupt handling (normal interrupt mode)

Data acquisition timed by internal timer

void IRQHandler (void) { if (GetITStatus (INTERRUPT_LINE)! = RESET) { /*Clearing the Interrupt pending bit from the Micro-controller*/ ClearITPendingBit (INTERRUPT_LINE);

/*Reading the Interrupt status register*/ STMPE812A_GetInterruptStatus (&Touch_Data [0]);

/*Reading the 4 bytes of x, y & z data from the register address of 0x44 to 0x47*/ I2C_Read_Data (STMPE812A_SLAVE_ADDR, STMPE812A_TSC_DATA, 4, &Touch_Data [1]);

/*Checking the bit 6(release bit) value from Interrupt status register goes low*/ if ((Touch_Data [0] & 0x40) == 0x00) { /*Sets the global variable (Is_Pen_Down) to handle the global variables (Touch_Data [1] to Touch_Data [4] i.e. 4 bytes of x, y & z data coordinates) in the main while loop*/

Is_Pen_Down = TRUE;

}

/*Handling Coordinates codes should be here */

} /*Checking the bit 6(release bit) value from Interrupt status register goes high*/

if ((Touch_Data [0] & 0x40) == 0x40)

{

/*Resets the global variable (Is_Pen_Down) to clear the point (x, y & z data coordinates) in the main while loop*/

Is_Pen_Down = FALSE;

}

}}

Data acquisition triggered by a write to “ACQ” bit

void IRQHandler (void) {

if (GetITStatus (INTERRUPT_LINE)! = RESET)

{

/*Clearing the Interrupt pending bit from the Micro-controller*/

ClearITPendingBit (INTERRUPT_LINE);

/*Reading the Interrupt status register*/

STMPE812A_GetInterruptStatus (&Touch_Data [0]);

/*Checking either the bit 0 or 1(touch bit or data bit) value from Interrupt status register goes high*/

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if (((Touch_Data [0] & 0x01) == 0x01) || ((Touch_Data [0] & 0x02) == 0x02))

{

/*Reading the 4 bytes of x, y & z data from the register address of 0x44 to 0x47*/

I2C_Read_Data (STMPE812A_SLAVE_ADDR, STMPE812A_TSC_DATA, 4, &Touch_Data [1]);

/* Sets the ACQ [4] in the TSC Control Register (0x40) */

STMPE812A_InitiateAcquisition ();

/* Waiting until the ACQ [4] in the TSC Control Register (0x40) goes low */

while (!STMPE812A_IsAcquisitionComplete ())

{}

}

/*Checking the bit 1(data bit) value from Interrupt status register goes high*/

if ((Touch_Data [0] & 0x02) == 0x02)

{

/*Sets the global variable (Is_Pen_Down) to handle the global variables (Touch_Data [1] to Touch_Data [4] i.e. 4 bytes of x, y & z data coordinates) */

Is_Pen_Down = TRUE;

/*Handling Coordinates codes should be here */

}

/*Checking the bit 6 (release bit) value from Interrupt status register goes high*/

if (((Touch_Data [0] & 0x40) == 0x40))

{

/*Resets the global variable (Is_Pen_Down) to clear the point (x, y & z data coordinates) in the main while loop*/

Is_Pen_Down = FALSE;

}

}}

Data acquisition using host-controlled sampling rate control

void IRQHandler (void) {

if (GetITStatus (INTERRUPT_LINE)! = RESET)

{

/*Clearing the Interrupt pending bit from the Micro-controller*/

ClearITPendingBit (INTERRUPT_LINE);

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/*Reading the Interrupt status register*/

STMPE812A_GetInterruptStatus (&Touch_Data [0]);

/*Checking either the bit 0 or 1(touch bit or data bit) value from Interrupt status register goes high*/

if (((Touch_Data [0] & 0x01) == 0x01) || ((Touch_Data [0] & 0x02) == 0x02))

{

/*Reading the 4 bytes of x, y & z data from the register address of 0x44 to 0x47*/

I2C_Read_Data (STMPE812A_SLAVE_ADDR, STMPE812A_TSC_DATA, 4, &Touch_Data [1]);

}

/*Checking the bit 1(data bit) value from Interrupt status register goes high*/

if ((Touch_Data [0] & 0x02) == 0x02)

{

/*Sets the global variable (Is_Pen_Down) to handle the global variables (Touch_Data [1] to Touch_Data [4] i.e. 4 bytes of x, y & z data coordinates) in the main while loop*/

Is_Pen_Down = TRUE;

/*Handling Coordinates codes should be here */

}

/*Checking the bit 6 (release bit) value from Interrupt status register goes high*/

if (((Touch_Data [0] & 0x40) == 0x40))

{

/*Resets the global variable (Is_Pen_Down) to clear the point (x, y & z data coordinates) in the main while loop*/

Is_Pen_Down = FALSE;

}

}}

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2.6.3 GPIO initialization and interrupt handling

The following is an example for GPIO initialization and interrupt servicing routine.

A: Initialization

void STMPE812A_GPIO_Initialization (void) {

/*Enabling the Soft Reset in the System Control Register (0x03)*/

STMPE812A_SoftReset ();

/*Enabling the GPIO Clock in the System Control Register (0x03)*/

STMPE812A_SetClock (STMPE812A_ENABLE, STMPE812A_GPIO_CLK);

/*Setting the Port - 2 as a special function in the Port Function Control Register (0x04)*/

STMPE812A_SetPortFunction (STMPE812A_PORT2, STMPE812A_PORT_FUNC_SPECIAL_FUNC);

/*Setting the Port - 1 as a GPIO Input in the Port Function Control Register (0x04)*/

STMPE812A_SetPortFunction (STMPE812A_PORT1, STMPE812A_PORT_FUNC_GPIO_IP);

/*Enabling the IO-1 [1] as GPIO Falling Edge Detection in the GPIO Falling Edge Detection Register (0x14)*/

STMPE812A_EnableGPIOFallingEdgeInterrupt (STMPE812A_IO1, TRUE);

/*Setting the INT_Mode [7] as ‘Normal Interrupt Mode’ in the Interrupt Control Register (0x08)*/

STMPE812A_SetInterruptMode(STMPE812A_INT_MODE_NORMAL);

/*Setting the INT_Type [1] as ‘Level Interrupt Type’ in the Interrupt Control Register (0x08)*/

STMPE812A_SetInterruptType (STMPE812A_INT_TYPE_LEVEL);

/*Enabling the Global Interrupt in the Interrupt Control Register (0x08)*/

STMPE812A_EnableGlobalInterrupt (TRUE);

/*Enabling the interrupt from the system related source of P1 to the host in the Interrupt Enable Register (0x09)*/

STMPE812A_EnableInterrupt (STMPE812A_INT_P1, TRUE);

}

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B: Interrupt handling

void IRQHandler (void) {

if (GetITStatus (INTERRUPT_LINE)! = RESET)

{

/*Clearing the Interrupt pending bit from the Micro-controller*/

ClearITPendingBit (INTERRUPT_LINE);

/*Checking the Interrupt Pin Status goes low*/

while ((GPIO_INTERRUPT->IDR & GPIO_PIN_INTERRUPT) == 0)

{

/*Reading the Interrupt status register*/

STMPE812A_GetInterruptStatus (&Touch_Data [0]);

/*Checking the bit 3(P1 bit) value from Interrupt status register goes high*/

if ((Touch_Data [0] & 0x08) == 0x08)

{

/*Printing“GPIO Falling Edge is Detected” on the monitor screen*/

printf (“GPIO Falling Edge is Detected”);

}

}}

2.6.4 ADC initialization and interrupt handling

The following is an example for ADC initialization and interrupt servicing routine.

A: Initialization

void STMPE812A_ADC_Initialization (void) {

/*Enabling the Soft Reset in the System Control Register (0x03)*/

STMPE812A_SoftReset ();

/*Enabling the ADC and GPIO Clocks in the System Control Register (0x03)*/

STMPE812A_SetClock (STMPE812A_ENABLE, STMPE812A_ADC_CLK|STMPE812A_GPIO_CLK);

/*Setting the Port - 2 as a special function in the Port Function Control Register (0x04)*/

STMPE812A_SetPortFunction (STMPE812A_PORT2, STMPE812A_PORT_FUNC_SPECIAL_FUNC);

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/*Setting the Port - 1 as an ADC Input in the Port Function Control Register (0x04)*/

STMPE812A_SetPortFunction (STMPE812A_PORT1, STMPE812A_PORT_FUNC_ADC_IP);

/*Setting the ADC_MODE [7] as 'One-shot capture', ADC_FREQ [5:4] as '15Ksamples/sec' and ADC_PORT in the ADC Control Register (0x20) respectively*/

STMPE812A_SetADC (STMPE812A_ADC_1_SHOT_CAPTURE, STMPE812A_ADC_FREQ_15K, STMPE812A_ADC_PORT);

/*Setting the INT_Mode [7] as ‘Normal Interrupt Mode’ in the Interrupt Control Register (0x08)*/

STMPE812A_SetInterruptMode(STMPE812A_INT_MODE_NORMAL);

/*Setting the INT_Type [1] as ‘Level Interrupt Type’ in the Interrupt Control Register (0x08)*/

STMPE812A_SetInterruptType (STMPE812A_INT_TYPE_LEVEL);

/*Enabling the Global Interrupt in the Interrupt Control Register (0x08)*/

STMPE812A_EnableGlobalInterrupt (TRUE);

/*Enabling the interrupt from the system related source of P1 to the host in the Interrupt Enable Register (0x09)*/

STMPE812A_EnableInterrupt (STMPE812A_INT_P1, TRUE);

/*Starting the ADC Conversion (Initiate Data Acquisition by setting the bit [6]) in the ADC Control Register (0x20)*/

STMPE812A_StartADC (TRUE);

}

Interrupt handling

void IRQHandler (void) {

if (GetITStatus (INTERRUPT_LINE)! = RESET)

{

/*Clearing the Interrupt pending bit from the Micro-controller*/

ClearITPendingBit (INTERRUPT_LINE);

/*Checking the Interrupt Pin Status goes low*/

while ((GPIO_INTERRUPT->IDR & GPIO_PIN_INTERRUPT) == 0)

{

/*Reading the Interrupt status register*/

STMPE812A_GetInterruptStatus (&Touch_Data [0]);

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/*Checking the bit 3(P1 bit) value from Interrupt status register goes high*/

if ((Touch_Data [0] & 0x08) == 0x08)

{

/*Getting the12 bits ADC data from the ADC Data Register (0x21 & 0x22) */

STMPE812A_GetADCData (&adcdata);

/*Printing the received “adcdata” value on the monitor screen*/

printf ("%ld\n\r", adcdata);

/*Starting the ADC Conversion (Initiate Data Acquisition by setting the bit [6]) in the ADC Control Register (0x20)*/

STMPE812A_StartADC (TRUE);

}

}}

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2.6.5 PWM initialization and interrupt handling

The following is an example for PWM initialization and interrupt servicing routine.

A: Initialization

void STMPE812A_PWM_Initialization (void) {

/*Enabling the Soft Reset in the System Control Register (0x03)*/

STMPE812A_SoftReset ();

/*Enabling the PWM and GPIO Clocks in the System Control Register (0x03)*/

STMPE812A_SetClock (STMPE812A_ENABLE, STMPE812A_PWM_CLK|STMPE812A_GPIO_CLK);

/*Setting the Port - 2 as a special function in the Port Function Control Register (0x04)*/

STMPE812A_SetPortFunction (STMPE812A_PORT2, STMPE812A_PORT_FUNC_SPECIAL_FUNC);

/*Setting the Port - 1 as a special function in the Port Function Control Register (0x04)*/

STMPE812A_SetPortFunction (STMPE812A_PORT1, STMPE812A_PORT_FUNC_SPECIAL_FUNC);

/*Setting the Burst_Length [1:0] as ‘8mS’ in the PWMClockDiv Register (0x50) */

STMPE812A_SetPWMBurstLengh (STMPE812A_PWM_BURSTLENGTH_8MS);

/*Setting the Div [4:0] value as ‘0’ in the PWMClockDiv Register (0x50) respectively*/

STMPE812A_SetPWMClockDivider (0);

/*Setting the Brightness [7:4] as ‘Duty Cycle Ratio 8: 8 (50.00%)’, BurstMultiplier [3:2] value as ‘1’ and Off_State [1] as ‘PWM Output “LOW” when PWM not running’ in the PWMControl1 Register (0x51) respectively*/

STMPE812A_ConfigurePWM (STMPE812A_PWM_DUTY_CYCLE_50_00, 1, STMPE812A_PWM_OFF_STATE_HIGH);

/*Setting the INT_Mode [7] as ‘Normal Interrupt Mode’ in the Interrupt Control Register (0x08)*/

STMPE812A_SetInterruptMode(STMPE812A_INT_MODE_NORMAL);

/*Setting the INT_Type [1] as ‘Level Interrupt Type’ in the Interrupt Control Register (0x08)*/

STMPE812A_SetInterruptType (STMPE812A_INT_TYPE_LEVEL);

/*Enabling the Global Interrupt in the Interrupt Control Register (0x08)*/

STMPE812A_EnableGlobalInterrupt (TRUE);

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/*Enabling the interrupt from the system related source of P1 to the host in the Interrupt Enable Register (0x09)*/

STMPE812A_EnableInterrupt (STMPE812A_INT_P1, TRUE);

/*Enabling the PWM Controller Sequence in the PWMControl1 Register (0x51)*/

STMPE812A_EnablePWM (TRUE);

}

B: Interrupt handling

void IRQHandler (void) {

if (GetITStatus (INTERRUPT_LINE)! = RESET)

{

/*Clearing the Interrupt pending bit from the Micro-controller*/

ClearITPendingBit (INTERRUPT_LINE);

/*Checking the Interrupt Pin Status goes low*/

while ((GPIO_INTERRUPT->IDR & GPIO_PIN_INTERRUPT) == 0)

{

/*Reading the Interrupt status register*/

STMPE812A_GetInterruptStatus (&Touch_Data [0]);

/*Checking the bit 3(P1 bit) value from Interrupt status register goes high*/

if ((Touch_Data [0] & 0x08) == 0x08)

{

/*Enabling the PWM Controller Sequence in the PWMControl1 Register (0x51)*/

STMPE812A_EnablePWM (TRUE);

}

}}

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Revision history AN3301

3 Revision history

Table 3. Document revision history

Date Revision Changes

14-Dec-2010 1 Initial release.

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AN3301

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Doc ID 18161 Rev 1 35/35

ST AN3301 Application note

Specifications and Main Features

Frequently Asked Questions

User Manual

1 Hardware

1.1 Typical application circuit and external components

Figure 1. Typical application schematic

1.2 Power supply

1.2.1 Power sequence (fail safe)

1.3 Power modes transition

1.4 Touchscreen tracks

1.4.1 Track resistance

Figure 2. Track resistance

1.5 Noise prevention

Figure 3. Noise prevention

1.6 Noise filtering

1.7 PWM controller

Figure 4. PWM LED driving configurations

1.8 ADC controller

1.9 GPIO output configurations

1.9.1 Push-pull

Figure 5. GPIO push-pull configuration

1.9.2 Open drain

Figure 6. GPIO open drain configuration (output low)

Figure 7. GPIO open drain configuration (output high)

2 Software

2.1 Touchscreen controller acquisition modes

2.1.1 Data acquisition by internal timer (ACQ_mode “00”)

Figure 8. Data acquisition by internal timer

2.1.2 Data acquisition by ACQ command (ACQ_mode “01”)

Figure 9. Data acquisition by ACQ command

2.1.3 Data acquisition by host read control (ACQ_mode “10”)

Figure 10. Data acquisition by host read command

2.2 Embedded data valid bit

Figure 11. TSC data register

2.3 Pen down interrupt mode

2.4 TSC_DATA read

2.5 Touchscreen controller sampling

Figure 12. Touchscreen controller sampling

2.6 Programming guide

2.6.1 Touchscreen initialization and interrupt handling (pen down mode)

2.6.2 Touchscreen initialization and interrupt handling (normal interrupt mode)

2.6.3 GPIO initialization and interrupt handling

2.6.4 ADC initialization and interrupt handling

2.6.5 PWM initialization and interrupt handling

3 Revision history