![]() ![]() ![]() ![]() Please switch the resistor to ON position only if the HAT is on one end of the bus line. 4) For the DIP switches I tried 2 sets of configuration: a) The suggested RS484 settings in the HAT manual for automatic send/receive control: Switch 1: 1-OFF 2-ON 3-ON 4-OFF Switch 2: 1-OFF 2-OFF 3-ON 4-ON Switch 3: 1-ON 2-OFF 3-ON 4-ON b) Switch 1: 1-OFF 2-ON 3-ON 4-OFF Switch 2: 1-OFF 2-OFF 3-ON 4-ON Switch 3: 1-OFF or ON* 2-OFF 3-OFF 4-OFF *Depending of the position of the RS422/RS485 HAT in the Modbus line you have to switch the terminating resistor ON or OFF. This seems like a feature the HAT should have? Wouldnt all Rs485 devices require some form of power? I realise maybe I should have got the stackable HAT and then i could use the 5v from that instead. I have a USB cable providing these, also plugged into the Pi. Do I need to get another plug with A B cables and solder a resistor between them to terminate the bus or will it work without, albeit in a sub-optimal way? 3) The WT901C requires 5v and Gnd but the HAT doesnt provide these. It has the same connector on the other side to chain devices together. 2) I assume this is OK for a proof of concept setup like this? The WT901C came with a single cable wired into a plug that fits in the side. I also don't have a terminating resistor at the end of the bus. a few cms long and not twisted or shielded. I only have the Pi, the HAT, and the WT901C connected together with AB wires that are just dupont wires - i.e. 1) is this normal for the Rx LED to remain constantly on? I would expect that Tx and Rx would flash on and off rather than be constantly on or off? I dont understand how to set DIP switch 3. If I do this the Rx LED on the HAT comes on and remains constantly on. I have a Raspberry Pi 4B with the HAT attached, and a "WT901C High Accuracy 9 Axis RS485 Modbus" accellerometer attached to the A and B terminals (with A and B swapped as per earlier comments about the labelling being reversed on the HAT). ![]() I'm not sure which part of the overall solution isn't configured right. I'm struggling to make the HAT work with AWS Greengrass and its Modbus component. I also spent a while figuring out the A and B terminal labels printed on the HAT are reversed. ![]()
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May 2023
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