ST AN3280 Application note

AN3280

Application Note

Displaying variable voltage on a bar of LEDs using STM8S-DISCOVERY

Application overview

This application note provides a short description of how to use the ADC, Timer and GPIO peripherals.

Once the STM8S105C6T6 has been powered-up through a USB cable connected to the host PC, the Timer triggers the ADC according to a user-defined period to convert the analog voltage provided by variable resistor RV1. The resulting average voltage measurement is represented on the LED bar.

Even though the STM8S-DISCOVERY is built around an STM8S105C6T6, it allows evaluation of the main features of all the STM8S MCUs.

Reference documents

■STM8S-DISCOVERY evaluation board user manual (UM0817).

■Developing and debugging your STM8S-DISCOVERY application code user manual (UM0834).

October 2010

Doc ID 17983 Rev 1

1/13

www.st.com

Contents	AN3280

Contents

1	Application description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .		5
	1.1	Hardware requirements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .	5
	1.2	Application schematic . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .	5
	1.3	Application principle . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .	6

2	Software description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .		7
	2.1	Application software flowcharts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .	9

2.1.1 Main loop flowchart . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 2.1.2 ADC1 interrupt routine . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10 2.1.3 TIM1 capture/compare interrupt . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11

3

Revision history . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

12

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AN3280	List of tables

List of tables

Table 1. Voltage and LED correspondence . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 Table 2. Document revision history . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12

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List of figures	AN3280

List of figures

Figure 1. Application schematic . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 Figure 2. ADC1 acquisition principle . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 Figure 3. Main loop flowchart. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 Figure 4. ADC1 EOC interrupt flowchart . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10 Figure 5. TIM1 capture/compare flowchart . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11

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