RAK5802 times out with RAK19011, RAK11200


I am trying to read data from a Modbus RTU slave using RAK5802 on a Dual IO RAK19011, but I only receive timeout errors.

Using the example code from RAKWireless GitHub, I receive the following response when I call try to read from the coils: Request result: 0xE4, Mem:339847. In the Modbus library the example code uses, 0xE4 corresponds to EX_TIMEOUT = 0xE4, // Custom. Operation not finished within reasonable time

I know the Modbus RTU slave is working correctly as I can read data from it on my PC using a Modbus RS485 to USB adaptor and Modbus Poll software.

I am using the following boards (my end goal is to read data from Modbus RTU and write the data to CAN bus):

  • RAK19011 Dual IO Base Board with Power Slot
  • RAK5802 RS485 Module 3PEAK TP8485E
  • RAK13006 CAN Bus Interface Microchip MCP2518FD
  • RAK11200 WiFi and BLE Espressif ESP32-WROVER
  • RAK19012 USB LiPo Solar Power Slot Module

Is there something I should configure differently in the example code since I am using RAK19011 Dual IO Base Board?

Thanks for your help,

Welcome to the forum @Unwritten6050

There are no special changes required for the Dual IO board, the IO slots are identical with the RAK19007.

Are there any RS485 devices connected to the RAK5802? If yes, what devices did you connect?

Hi @beegee,

The issue turned out the be a dead spot on the breadboard I was using to connect the RS485 device to the RAK5802. Once I swapped out the breadboard, I was able to read from Modbus RTU perfectly.

Thanks for your help :slight_smile:

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