Logging 40 holding registers from a solar inverter over RS485 (9600 baud, 8N1) Old behavior (v8.x): Frequent “Bytes missing” errors, especially during polls every 200 ms. New behavior (v9.2.1 build 1824): Rock-solid for 72 hours of continuous polling.
EMI from VFDs and missing termination resistor.
A normal Modbus RTU read response looks like this: [Slave ID] [Function Code] [Byte Count] [Data Bytes...] [CRC Low] [CRC High] .
Ensure the following settings match exactly between Modbus Poll (Connection > Connect) and your slave device: modbus poll bytes missing error fixed
The "bytes missing" error in Modbus Poll is most often a symptom of a configuration mismatch or a hardware problem. By methodically working through these steps—starting with verifying serial settings and physical connections, then moving to simpler checks like power cycling and project file recreation before finally using advanced diagnostics like a COM monitor—you can successfully resolve the issue and establish reliable communication.
Fixing "Bytes Missing" is rarely about the software being "broken"—it’s about harmonizing the speed of light with the limitations of copper and silicon. Once you find that sweet spot of timing and shielding, the error vanishes like smoke.
Fixing this problem requires a systematic approach to check your hardware wiring, serial settings, and device response times. Step 1: Verify and Match Serial Communication Settings Logging 40 holding registers from a solar inverter
Ground the cable shield at to avoid ground loops.
If the master and slave are not running at the exact same baud rate, parity, or stop bits, the data will be interpreted incorrectly, causing the serial port to cut off the message prematurely.
Requesting too many registers in a single Modbus function code call can exceed the slave device’s buffer capacity. A normal Modbus RTU read response looks like
Install a across the A (+) and B (-) lines at the physical beginning and absolute end of your RS485 bus.
Ground the cable shield at to avoid creating ground loops.