RS485 direction control from GPIO for /dev/ttyS4?

#1

Hi,
pls advise, is there a way to get RS485 direction control signal out of GPIO when /dev/ttyS4 (gpio pins 15, 16) is used to communicate with RS485 bus?

That control signal should be high when transmitting. It is possible to create such a direction control signal with external logic based on TX from Khadas, but it would much simpler if one of the GPIO pins would be usable as direction control output.

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#2

It should works, but you might need a TTL to RS485 Two-way Converter.

You can take a try :slight_smile:

Have fun!

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#3

I have that that (TTL/RS485 interface) on the IO-board, connected to the 40-pin header of VIM. But there the RS485 direction control signal is calculated by a (PIC) microcontroller, taking the communication parameters into account. Was just wondering if I could skip that in some future designs…

Anyway, no problem, I can always use an USB-to-RS485 cable to get RS485.

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#4

Can you just show us the schematic of the IO board?

Not quite clear on this, can you specify more information?

Good day!

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#5

related to the rs485 driver circuit, there are 3 signals. TX, RX and direction control, named P1.0 on the diagram below.
rs485

was just thinking that it would be nice if the missing direction signal would become available from gpio.

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