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Xinyuan-LilyGO / LilyGO-T-ETH-Series

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T-POE-PRO - signal RS485 ground and shield ground (MGND or DGND) #76

Open philippesikora opened 1 month ago

philippesikora commented 1 month ago

A galvanic TTL to RS485 device (Waveshare) is connected to T-POE-PRO (NOT opto-isolated) with a shielded cable.("2 wires + Ground + shield"). Where to connect signal RS485 ground and shield ground (MGND or DGND) ?

semi_isolated_RS485

lewisxhe commented 1 month ago

The signal ground is DGND, and the metal shell ground is connected to MGND

philippesikora commented 3 weeks ago

I'm using the device Waveshare TTL To RS485 (C) Galvanic Isolated Converter as RS485 master (Rx, Tx, Vcc, GND) connected to T-POE-PRO (485_A, 485_B, DGND) with 120 ohms resistor between 485_A and 485_B) as RS485 slave. I also added a 10K pull-up resistor to the first pin of the MAX13487E chip to the eighth pin of the MAX13487E chip. I'm testing with RS485_Slave.ino example, but no information is received while RS485 master is sending data (green light on Waveshare device when data are sent). Do you know have any ideas of this issue with T-POE-PRO?

philippesikora commented 1 week ago

Could you confirm if I have to add 10K pull-up resistor and if 120 ohms resistor between 485_A and 485_B is needed and DGND connected to GND? Thank you