@peekay123 The Modbus master library you created https://github.com/pkourany/ModBusMaster uses a RS-485 communication (Modbus RTU). I can see you can set the number of the serial port. However, I am wondering where you define the pin of the spark/photon that controls the lines (DE / REneg)? Since RS…

@peekay123 I tried compiling your port locally, but was getting an “Error: You are building with the Photon as a target”. I commented out the lines in ModbusRtu.h that throw this error: #if PLATFORM_ID == 0 // Core #error "*** You are building with the Core as a target ***" #elif PLATFORM_ID == 6…

@beck , that looks like code I left behind for testing! Those should be warnings, not errors. Oy!

@beck , @peekay123 ,I connected my USB-FTDI cable to the RX/TX pins and was able to query some input registers. I moved millis() to the first word of the array so I can at least watch something move. This evening I will try hooking up my MAX485 chips and see if I can achieve a multidrop system (and …

@adamg thanks! I have this running right now as well, seems like all the slave function codes work. The only thing that I found a bit confusing is that in the slave, the Modbus data address offset isn’t implemented (if it were, coils 0000-270E would map to memory locations 1-9999). Consequently, in…

@beck , Sorry for the delay. I too have been using the library for a few days and noticed the same offset/mapping issues that you speak of. However to be honest, it will still work fine for my application as I will be transferring 16 words at max. I will be bit-packing my coils into holding regist…

Hello @peekay123 , I tried to import the the library ModBusMaster in the WEB IDE but does not compile. Also I tried with manual input files but without success. I try and ModBus_RS485_Slave library and compile without problem.It requires a small modification of code to support multiple serial por…

@developer_bt , neither library has been updated in a while and they are not Libraries v2.0 compatible. I’ll try and spend some time today to review them both.

@developer_bt , there is already a ModBusMaster library on the IDE. Have you tried it?

@peekay123 Yes I tried to import the the library ModBusMaster in the WEB IDE but does not compile. The same happens with manual input C++/h files. Processing /workspace/modbus.ino make -C ../modules/electron/user-part all make[1]: Entering directory '/firmware/modules/electron/user-part' make -C …

@developer_bt , the errors are caused by the Arduino pre-processor problems. If you compile for system firmware v 0.6.0, it will work.

RS-485 modbus library

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RS-485 modbus library

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