Serial Expansion HAT User Manual
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Serial Expansion HAT
User Manual
OVERVIEW
Serial Expansion HAT for Raspberry Pi, I2C Interface, Provides 2-ch UART and 8 GPIOs
FEATURES
⚫ Raspberry Pi connectivity, compatible with Raspberry Pi Zero/Zero W/Zero
WH/2B/3B/3B+
⚫ Onboard SC16IS752, expands 2-ch UART and 8 programmable GPIO through I2C,
no extra pin required
⚫ It is stackable up to 16 modules by setting the address jumper, that means up to
32-ch UART
⚫ Onboard multi LEDs for indicating the UART working status
⚫ Reserved I2C control pins, allows to work with other control boards
⚫ Comes with development resources and manual (examples in C and python)
SPECIFICATION
⚫ Operating voltage: 3.3V
⚫ Expansion chip: SC16IS752
⚫ Control interface: I2C
⚫ Dimension: 65mm x 30mm
⚫ Mounting hole size: 3.0mm
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CONTENT
Overview ....................................................................................................................................................... 1
Features ................................................................................................................................................ 1
Specification ....................................................................................................................................... 1
Hardware ...................................................................................................................................................... 4
Pinout ........................................................................................................................................... 5
LED ................................................................................................................................................. 5
I2C device address setting .................................................................................................... 6
How to use .................................................................................................................................................. 7
Download Demo codes .......................................................................................................... 7
Libraries Installation (Require network) ........................................................................... 8
Enable I2C Interface ................................................................................................................. 8
Demo codes .............................................................................................................................................. 11
C/GPIO/ .............................................................................................................................................. 11
Files .............................................................................................................................................. 12
Codes Analysis ......................................................................................................................... 12
C/UART/ ............................................................................................................................................. 13
Files .............................................................................................................................................. 14
Send code ................................................................................................................................. 15
Receive code ............................................................................................................................ 16
python................................................................................................................................................. 17
Files .............................................................................................................................................. 17
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Receive code ............................................................................................................................ 17
Send code ................................................................................................................................. 18
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HARDWARE
The SC16IS752 is an I2C-bus/SPI bus interface to a dual-channel high
performance UART. It also provides the application with 8 additional programmable
I/O pins. This module uses I2C interface by default, and its device address is hardware
configurable by A0 and A1.
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PINOUT
PIN
Description
3V3
3.3V
GND
Ground
TXDA
Transmit end of Channel A
RXDA
Receive end of Channel A
RTSA
Request to send of Channel A
CTSA
Clear to send of Channel A
TXDB
Transmit end of Channel B
RXDB
Receive end of Channel B
RTSB
Request to send of Channel B
CTSB
Clear to send of Channel B
LED
PWR: Power indicator
TXDA: Channel A transmit indicator
RXDA: Channel A receive indicator
TXDB: Channel B transmit indicator
RXDB: Channel B receive indicator
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I2C DEVICE ADDRESS SETTING
I2C device address can be configured by changing status of A0 and A1, that is welding
0R resister to them according to this table:
For details, please refer to datasheet: Page39
The I2C address in table are 8bits, however, the actual address is 7bits, you need to
right-shift one bit to get the actual I2C address. For example, if you connect A1 and A0
to Vdd, the address of module is 0x90 according to the table, to get the actual address
you need to right-shift the data from 1001 000X to 100 1000, that is 0x48.
【Note】This module A0 and A1 are default welded to 3.3V, with I2C address 0x48
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HOW TO USE
DOWNLOAD DEMO CODES
Visit WaveShare Wiki, search with key words “Serial Expansion HAT”, open it and
download demo codes:
Extract and copy folders to Raspberry Pi.
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LIBRARIES INSTALLATION (REQUIRE NETWORK)
1 Install wiringPi
1.1 Open Terminal of Raspbian(Ctrl+T), clone wiringPi from github
git clone git://git.drogon.net/wiringPi
1.2 Install
cd wiringPi
./build
2 Install python libraries
2.1 Install python-dev
sudo apt-get install python-dev
2.2 Install RPi.GPIO
sudo apt-get install python-rpi.gpio
2.3 Install smbus, which is I2C interfaces library
sudo apt-get install python-smbus
2.4 Install spidev, which is SPI interfaces library
sudo apt-get install python-spidev
ENABLE I2C INTERFACE
1 Execute command: sudo raspi-config
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2 Choose: Interfacing Options->I2C->Yes
3 Append this line to end of /boot/config.txt file: sudo nano /boot/config.txt
dtoverlay=sc16is752-i2c,int_pin=24,addr=0x48
# addr is different according to status of A0/A1, default 0X48
4 reboot
sudo reboot
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5 After rebooting, you can execute command: ls /dev to check if SC16IS752 has
been enabled to kernel.
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DEMO CODES
We provide demo codes for this module, based on C codes and python.
C/GPIO/
There are 8 GPIO which are expanded. You can connect LEDs to these GPIOs when
testing.
1. Open the folder of the demo code
cd Serial_Expansion_HAT_code/c/gpio/
#change the path of you didn’t put the code in /home/pi
2. Compile and run the code
make
sudo ./main
3. After running the demo code, code will light on/off 8 LEDs one by one.
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FILES
main.c: main function
SC16IS752GPIO.c(.h): functions control IO
Makefile: Codes compilation
CODES ANALYSIS
Functions in SC6IS752GPIO.c:
int GPIOExport(int Pin): Export GPIO
int GPIOUnexport(int Pin): Unexport GPIO
int GPIODirection(int Pin, int Dir): Set direction of GPIO
int GPIORead(int Pin): Read value of GPIO
int GPIOWrite(int Pin, int value), Write value to GPIO
Files used by these functions are all in /sys/class/gpio, and according to use guide, the
GPIO generated by SC16IS752 is coded 504. So, the codes of 8 GPIO are from 504 to
511.
Functions in main.c:
GPIO_Init(): Initialize 8 GPIO.
GPIO_Exit(): Unexport GPIOs
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C/UART/
To test UART demo code, you need to use two Serial Expansion HAT and two
Raspberry Pi, one is set as receiver and another is sender. You can also connect with
serial module to PC if you have no other Raspberry Pi and Expansion HAT. Connect
RXB of Serial Expansion HAT to TXB/TX of other module, and TXB of Serial Expansion
HAT to RXB/RX of another module.
1. Open the folder of code
cd Serial_Expansion_HAT_code/c/uart/
#change the path of you didn’t put the code in /home/pi
2. Two codes, receiver and sender, choose the one you want to run
cd receive/
# cd send/
3. Compile and run the code
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make
sudo ./uart_receive
# sudo ./uart_send
4. After running the code. Receiver: keep receiving and print data received; Sender:
send characters
FILES
/receive:
Makefile: Code compilation, execute command make to compile project
uart_receive.c: Receive function
uart_receive: Executable file, generated after command make
/send:
Makefile: Code compilation, execute command make to compile project
uart_send.c: Send function
uart_send: Executable file, generated after command make
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SEND CODE
1. Initialize wiringPi
if(wiringPiSetupGpio() < 0) { //use BCM2835 Pin number table
printf("set wiringPi lib failed !!! \r\n");
return 1;
} else {
printf("set wiringPi lib success !!! \r\n");
}
2. Open serial
int fd;
if((fd = serialOpen (UART_DEV1, 115200)) < 0) {
printf("serial err\n");
return -1;
}
3. Clear buffer
serialFlush(fd);
serialPrintf(fd,"\r");
4. Send a string
char *buf = "abcdefgh";
serialPuts(fd, buf);
5. Close serial
serialClose(fd);
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RECEIVE CODE
1. Initialize wiringPi
if(wiringPiSetupGpio() < 0) { //use BCM2835 Pin number table
printf("set wiringPi lib failed !!! \r\n");
return 1;
} else {
printf("set wiringPi lib success !!! \r\n");
}
2. Open serial
if((fd = serialOpen (UART_DEV2, 115200)) < 0) {
printf("serial err\n");
return -1;
}
#define UART_DEV1 "/dev/ttySC0"
#define UART_DEV2 "/dev/ttySC1"
3. Receive and print
for (;;) {
putchar(serialGetchar(fd));
}
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PYTHON
1. Open the folder of code
cd Serial_Expansion_HAT_code/pythont/
#change the path of you didn’t put the code in /home/pi
2. Compile and run
make
sudo python receive.py
#or sudo python send.py
FILES
【Note】Only serial codes provided
RECEIVE CODE
1. Open serial
ser = serial.Serial("/dev/ttySC1",115200,timeout=1)
2. Clear buffer
ser.flushInput()
3. Read data
ser.inWaiting()
4. Read specified bytes of data
ser.read(ser.inWaiting())
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SEND CODE
1. Open serial
ser = serial.Serial("/dev/ttySC1",115200,timeout=1)
2. Define data sent
ser = serial.Serial("/dev/ttySC1",115200,timeout=1)
3. Write the data to serial
ser.write(command)
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