Go to Windows Device Manager > Ports > COM Port > Advanced. Try lowering the Transmit and Receive FIFO buffers. This forces the driver to process smaller chunks of data more frequently, preventing byte loss. 5. Check Slave ID and Register Limits
Some older PLCs or sensors need a "breather" between requests. Set a delay between polls of at least 20–50ms . 3. Verify Serial Port Settings
Increase this from the default (usually 1000ms) to 3000ms to see if the error clears. modbus poll bytes missing error fixed
On long RS-485 runs, you must have a 120-ohm resistor at both ends of the bus to prevent signal reflection. Without these, bits get "smeared," and the software interprets them as missing data.
Ensure your Data+ (A) and Data- (B) lines aren't swapped. Go to Windows Device Manager > Ports > COM Port > Advanced
In the Modbus Poll software, the default timeout settings might be too aggressive for your hardware, especially if you are using wireless bridges or slow cellular gateways.
A single mismatch here will cause the Master to misinterpret the incoming data stream as "missing" or "corrupt." or Ethernet-based industrial automation
If you ask for 100 registers but the slave only has 50, the slave might send an exception code or a truncated packet.
Don't poll too fast. If your scan rate is 100ms but the device takes 200ms to respond, the packets will collide. 6. Eliminate EMI (Electromagnetic Interference)
If you are working with RS-485, RS-232, or Ethernet-based industrial automation, few things are as frustrating as the error. You’ve set up your slave ID, matched your baud rate, and hit "Connect," only to see a communication breakdown.