1.2 KiB
1.2 KiB
modbusmaster
Disable Bluetooth on RPi3
Add at the end of /boot/config:
dtoverlay=pi3-disable-bt
Remove mentions of serial0 from /boot/cmdline.
Enable rs485 mode
Use the submodule rpirtscts to enable to alternate functions of the related pins at the RPi MCU. It is submoduled here, can be found directly at https://github.com/mholling/rpirtscts
cd rpirtscts
gcc -o rpirtscts rpirtscts.c
sudo ./rpirtscts on
This needs to be done at every boot.
Kudos to danjperron, cmp. https://www.raspberrypi.org/forums/viewtopic.php?f=98&t=224533&hilit=rs+485#p1383709
Pinout
Find a good pinout diagram at https://raw.githubusercontent.com/ppelleti/hs-wiringPi/master/pin-diagram.png.
TX is at GPIO14, RX is at GPIO15 and RTS (control line for transmitter enable) is at GPIO17.
Python snippet to test
import serial.rs485
ser=serial.rs485.RS485(port='/dev/ttyAMA0',baudrate=9600)
ser.rs485_mode = serial.rs485.RS485Settings(False,True)
ser.write('a test'.encode('utf-8'))
Find an signal screenshot here:
Channel 1 in yellow has the TX line, channel 3 in purple has the RTS (transmitter enable line).