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I have a "big" Problem.
I would like to use the MAX485 for Modbus RTU on the UART Port (GPIO14 and 15). Everything is fine but for the MAX485 I need to change the direction (transmit or receive) with a pin.
If this GPIO pin is high i can send through the MAX485. If this GPIO Pin is low than the MAX485 can receive.
Now i have the Problem that can´t get any direction variable from the Modbus library to toggle this Pin so im stuck at the moment.
Has someone maybe any idea
Greetings Christoph
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I'm not really sure, but using MAX 485 on the tty is not really possible without having
handshake pins to give the direction. To workaround this by a kind of own implemented mechanism
will not lead to a reliable solution.
I would recommend to use a ready to use USB to RS485 Adapter instead implement this with a huge effort.
Maybe I am totally wrong and someone could give us a hint how to solve this with a MAX485 circuit.
Best Regards
Edwin
If you would like to refer to this comment somewhere else in this project, copy and paste the following link:
Hello
I have a "big" Problem.
I would like to use the MAX485 for Modbus RTU on the UART Port (GPIO14 and 15). Everything is fine but for the MAX485 I need to change the direction (transmit or receive) with a pin.
If this GPIO pin is high i can send through the MAX485. If this GPIO Pin is low than the MAX485 can receive.
Now i have the Problem that can´t get any direction variable from the Modbus library to toggle this Pin so im stuck at the moment.
Has someone maybe any idea
Greetings Christoph
Hello Christoph,
I'm not really sure, but using MAX 485 on the tty is not really possible without having
handshake pins to give the direction. To workaround this by a kind of own implemented mechanism
will not lead to a reliable solution.
I would recommend to use a ready to use USB to RS485 Adapter instead implement this with a huge effort.
Maybe I am totally wrong and someone could give us a hint how to solve this with a MAX485 circuit.
Best Regards
Edwin
Hi Christoph,
maybe this links give more information at least an better explanation:
http://www.raspberrypi.org/forums/viewt ... 85#p514164
https://github.com/mholling/rpirtscts
Regards
Edwin