Mesa modbus and pktUart

The signals on A/B do not look right.
When undriven, A _must_ be higher than B
(or the VFD will receive garbage)


Can you scope TXEN and TXdata at the adapter pins?

 

Close Up of two signals together :

 

Donno wrote:

Can you give me an example please of ntxen in my use case ?

OPortTag & x"00" & PktUARTTTag & PktUTDrvEnPin,
 

IOPortTag & x"00" & PktUARTTTag & PktUTNDrvEnPin,

Is that TXEN at the adapter or direct from the 7I92
(the adapter needs active high TXEN)

​​​​​​Txen is from 7i92 to 74hc04 then to DE pin i see i mixed my tx an txena pin on picture image missing /media/kunena/emoticons/blink.png

OK so if TXEN is high during transmission (at the MAX485 DE pin)
That's correct

So if the rest of the wiring is OK (and the A/B lines idle with A high and B low)
you should be closer, though there could also be protocol errors or perhaps
address errors if the drive does not respond

You could check TXEN and RXData (RXData should echo TXData if everything is OK)