Template: Serial Expansion HAT User Mnaual
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 working 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 × 30mm
- Mounting hole size：3.0mm
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.
PINOUT
| PIN | Description |
| 3V3 | 3.3V |
| GND | Ground |
| TXDA | Transmit pin of CHA |
| RXDA | Receive pin of CHA |
| RTSA | Receive request of CHA |
| CTSA | Transmit request of CHA |
| TXDB | Transmit pin of CHB |
| RXDB | Receive pin of CHB |
| RTSB | Receive request of CHB |
| CTSB | Transmit request of CHB |
LED
PWR: Power indicator
TXDA: Trasmint indicator of CHA
RXDA: Receive indicator of CHA
TXDB: Transmit indicator of CHB
RXDB: Receive indicator of CHB
I2C Address Configuration
A0, A1 are used to control the I2C address of device, you can change them by soldering 0ohm resistors acccording the table:
详见datasheet:Page39
The I2C addresses in the 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 the 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
In theory, you can connect 32 devices to the same developer board by changing address.
If you bought the old version which is produced before 20191231, the interrupt pin is connected to GPIO of PI directly, you can only wiring the devices for stacking multi-devices.
If you buy the new version which is produced after 10291231, the interrupt pin is configurable by soldering resistors. Supports up to 5 devices by changing the pin, if you want to stack more than five devices, you need to wires them by cable.
Working with Raspberry Pi
Enable I2C Interface
Open a terminal and run the following commands:
sudo raspi-config Choose Interfacing Options -> I2C -> Yes.
Reboot Raspberry Pi:
sudo reboot
Install Libraries
Install Library
If you use the bookworm system, you can only use lgpio library, bcm2835 and wiringPi can't be installed and used.
BCM2835
#Open the Raspberry Pi terminal and run the following command wget http://www.airspayce.com/mikem/bcm2835/bcm2835-1.71.tar.gz tar zxvf bcm2835-1.71.tar.gz cd bcm2835-1.71/ sudo ./configure && sudo make && sudo make check && sudo make install # For more, you can refer to the official website at: http://www.airspayce.com/mikem/bcm2835/
WiringPi
#Open the Raspberry Pi terminal and run the following command cd sudo apt-get install wiringpi #For Raspberry Pi systems after May 2019 (earlier than that can be executed without), an upgrade may be required: wget https://project-downloads.drogon.net/wiringpi-latest.deb sudo dpkg -i wiringpi-latest.deb gpio -v # Run gpio -v and version 2.52 will appear, if it doesn't it means there was an installation error # Bullseye branch system using the following command: git clone https://github.com/WiringPi/WiringPi cd WiringPi . /build gpio -v # Run gpio -v and version 2.70 will appear, if it doesn't it means there was an installation error
lgpio
#Open the Raspberry Pi terminal and run the following command wget https://github.com/joan2937/lg/archive/master.zip unzip master.zip cd lg-master sudo make install # You can refer to the official website for more: https://github.com/gpiozero/lg
- python
sudo apt-get install python-dev sudo apt-get install python-rpi.gpio sudo apt-get install python-smbus
Configuration
- Append the line below to /boot/config.txt file:
sudo nano /boot/config.txt # addr shoube the same as the actual setting of A0A1, default 0X48 dtoverlay=sc16is752-i2c,int_pin=24,addr=0x48 # reboot sudo reboot
- After rebooting, you can execute the command: ls /dev to check if SC16IS752 has been enabled to kernel：
GPIOchip is the driver of 8 GPIO.（It maybe gpiochip3 or gpiochip2 according to different versions of OS）, ttysc0 and ttysc1 is the driver of serial ports.
You cannot directly stack the devices for multi-connecting because they use the same interrupt pin.
You need to wire the devices by cable or change the resistors, and modify the config.txt file:
dtoverlay=sc16is752-i2c,int_pin=xx,addr=0x48
xx is the actual BCM code of the interrupt pin.
Testing
Download demo ocdes
wget http://www.waveshare.com/w/upload/b/ba/Serial_Expansion_HAT_code.tar.gz tar zxvf Serial_Expansion_HAT_code.tar.gz sudo chmod 777 -R Serial_Expansion_HAT_code cd Serial_Expansion_HAT_code
Test Serial port
- c codes, baud rate is default 115200
#Send data via Serial A cd c/uart/send make clean make sudo ./uart_send
#Receive data via Serial B cd c/uart/receive/ make clean make sudo ./uart_receive
- Test
You can connect the TXDA to RXDB, RXDA to TXDB, open a terminal and one is set for transmit codes and another is set for receive codes.
Expected result:After running the code. Receiver: keep receiving and print data received; Sender: send characters。
If you test the device with external serial device, the GND should be connected for properly using.
- python, default baud rate 115200
cd python/Uart/ #Send data by Serial A sudo python send.py #Receive data by Serial B sudo python receive.py
Expect result: After running the code. Receiver: keep receiving and print data received; Sender: send characters
Test GPIO
- c语言
cd c/gpio/ make clean make sudo ./main
运行程序后，程序会翻转GPIO0的电平，如果在GPIO0上接上LED灯，会发现LED灯闪烁
- python
cd python/GPIO sudo python gpio.py
Expected result: The level of the GPIO0 is toggled for five times, GPIO1 is set as input, you can connect GPIO1 to 3.3V or GND to check the data.
Multi-devices
If you want to stack multi devices for using more Serail port, please follow the guides below.
Install i2c-tools and check the i2c address:
sudo apt-get install i2c-tools
Check i2c address with the following command:
sudo i2cdetect -y 1
If there is only one Serial Expansion HAT, it should be as figure:
The address is UU but not 0x48, it means that the driver has been enabled in OS and you can find ttySC* devices in /dev directory.其
If you want to stack another Serial Expansion HAT, you need to modify the address setting and INT pin of the second boars firs. For example：INT PIN -> P23,I2C Address: A0->GND:
After modifying, you can stack the boards and run the following commands
The new boards is recognized as 0x49. You also need to add setting line to config.txt file:
sudo nano /boot/config.txt
Add the following line and save：
dtoverlay=sc16is752-i2c,int_pin=23,addr=0x49
Reboot
sudo reboot
Check the devices with commands:
Because only five INT settings are available onboard, you can only stack five boards with the method above. If you want to connect more devices, you need to change and connect them by cable.