Modbus Poll Bytes Missing Error Fixed //top\\

Disconnect the slave device and short the TX+ and RX- pins on your RS485 converter. Send a Modbus request. If you receive an echo, your serial port and cable are fine. If not, the issue is hardware-related.

Increase the Response Timeout in your Connection Setup. Giving the device an extra 500ms can often bridge the gap. modbus poll bytes missing error fixed

One of the most common reasons for missing or corrupted bytes is your converter "echoing" the master’s request back to itself. Disconnect the slave device and short the TX+

, you know how frustrating it is. This error essentially means the master received a response, but it was shorter than the expected packet length based on your request. Here is a breakdown of why this happens and how to fix it. 1. The "Echo" Problem (RS-485) If not, the issue is hardware-related

Increase the "Response Timeout" setting in Modbus Poll (under Connection -> Connection Setup) to allow more time for the slave device to respond, especially if the device is slow or on a high-latency network. Increase Inter-frame Delay:

Use a converter with an FTDI chip or an "auto-direction" circuit. If you’re stuck with what you have, try decreasing the Baud Rate . Lower speeds are more forgiving of poor hardware timing.

Ensure your port number matches the gateway (common ports are 502 or 9999). 2. Timing and Timeout Issues