we are using ST3485ECDR in one of our RS485 communication. one board is operating at 5V and one more board is operating at 3.3V. But sometimes last byte of our packet is missing. what will be the issue.

[SLV.1]

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[Peter BENSCH]

Welcome, @SLV.1​, to the community!

As the number 3 in the component number shows, the ST3485ECDR is intended for 3.3V supply voltage and not for 5V.

Regards

/Peter

[SLV.1]

Hi Peter

Sorry we are using ST3485ECDR and ST485ECDR as 3.3V and 5V respectively. But while sending command from ST3485ECDR to ST485ECDR we are missing last byte of data. We connected 3 individual boards with ST485ECDR and one master ST3485ECDR in daisy chain mode.

[Peter BENSCH]

As you know, RS485 uses a differential transmission method that is independent of the supply voltage. It is also serial so that individual bytes are not simply lost.

Missing packets can usually be found in the connected controllers (FIFOs, software, protocols/handshake, etc). You could also use a logic analyzer to see if the data is being sent to the transceiver at all.

Regards

/Peter