PicoScope 7 Software
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Modbus reading different to RS485 UART
Modbus reading different to RS485 UART
Hi All,
Unfortunatly I am too stupid to work this out myself...
So here is my issue:
https://gyazo.com/546c69982c6cf7b9d90b41724bc0ecbf
The top and middle signal is the math channel (A-B). The top one decoded with modbus (not working) the middle with UART (working correctly).
The bottom shows the original signal.
I am running modbus poll on the right hand side which should be sending a modbus correct modbus packet.
my modbus decode is set to 4.8k baud, parity none and one ID byte.
I have checked other posts on the forum which people mention a similar issue where someone said the issue was them not having a long enough inter-frame delay. However as I am using a modbus packet generator I'd expect this to be correct.
Any takers?
Unfortunatly I am too stupid to work this out myself...
So here is my issue:
https://gyazo.com/546c69982c6cf7b9d90b41724bc0ecbf
The top and middle signal is the math channel (A-B). The top one decoded with modbus (not working) the middle with UART (working correctly).
The bottom shows the original signal.
I am running modbus poll on the right hand side which should be sending a modbus correct modbus packet.
my modbus decode is set to 4.8k baud, parity none and one ID byte.
I have checked other posts on the forum which people mention a similar issue where someone said the issue was them not having a long enough inter-frame delay. However as I am using a modbus packet generator I'd expect this to be correct.
Any takers?
Re: Modbus reading different to RS485 UART
Can you post the .psdata file ?
Benno
Benno
Re: Modbus reading different to RS485 UART
I worked out what I was doing wrong.
Modbus pol allows you to choose between 1 and 2 stop bits (mine was set to 1).
Picoscope seems to autoset this. From what I can find the modbus standard says when you aren't using parity bits you should always have 2 stop bits. I guess that is why there is no option to change it.
Thanks anyway!
Modbus pol allows you to choose between 1 and 2 stop bits (mine was set to 1).
Picoscope seems to autoset this. From what I can find the modbus standard says when you aren't using parity bits you should always have 2 stop bits. I guess that is why there is no option to change it.
Thanks anyway!