56 lines
1.5 KiB
Markdown
56 lines
1.5 KiB
Markdown
# modbusmaster
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## Disable Bluetooth on RPi3
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Add at the end of `/boot/config`:
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dtoverlay=pi3-disable-bt
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Remove mentions of `serial0` from `/boot/cmdline`.
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## Enable rs485 mode
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Use the submodule rpirtscts to enable to alternate functions of the related
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pins at the RPi MCU. It is submoduled here, can be found directly at https://github.com/mholling/rpirtscts
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cd rpirtscts
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gcc -o rpirtscts rpirtscts.c
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sudo ./rpirtscts on
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This needs to be done at every boot.
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Kudos to danjperron, cmp. https://www.raspberrypi.org/forums/viewtopic.php?f=98&t=224533&hilit=rs+485#p1383709
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(Note, please: This software is under the GPL 3.0 license. However, I do not derive from this software, I use it in an unchanged way. It is not integrated into my sources, it just needs to be called once the RPi has booted.)
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## Pinout
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Find a good pinout diagram at https://raw.githubusercontent.com/ppelleti/hs-wiringPi/master/pin-diagram.png.
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TX is at GPIO14, RX is at GPIO15 and RTS (control line for transmitter enable) is at GPIO17.
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## Schematics
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## Python snippet to test
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(See also `./snippets/test1.py`.)
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import serial.rs485
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ser=serial.rs485.RS485(port='/dev/ttyAMA0',baudrate=2400)
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ser.rs485_mode = serial.rs485.RS485Settings(False,True)
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ser.write('a test'.encode('utf-8'))
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Find an signal screenshot here:
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Channel 1 in yellow has the TX line (GPIO14), channel 3 in purple has the RTS (GPIO17, transmitter enable line).
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