Flow Control with RTS pulled HIGH

[connectedthings]

Have been running with a USB -> RS485 adapter on a Rpi for a while now without issues. This adapter supports ADDC or at least it works with that config.

Am now busy trying a RS485 Module ( TTL -> RS485 based on MAX481 chipset) directly connected to Rpi serial0 on GPIO 8 & 10, so no flow control. RTS is pulled high on the module itself and I can't get it to communicate.

Would I have to use file based flow control in this case?

[3cky]

Since RS-485 protocol is half-duplex, any module implementing it should have RX/TX mode switching circuit, either ADDC or connected to some RPi GPIO pin. And yes, in the second case you can use mbusd file-based direction control. But make sure you have a logic level shifter between RPi and MAX481, since RPi uses 3.3V logic which is incompatible with 5V TTL.

[stale]

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