connecting Pyprofibus with DP/PA coupler to communcate with PA devices (Invalid telegram format)
Kaz040 opened this issue · comments
Hello.
to start with, I am a novice in Profibus. I am working on a project to connected pyprofibus to DP/PA coupler so that i can communicate with some PA devices through it. I have been faced with some problem which I would really appreciate if i can get some help to start.
The main error i am getting now is
PHY-serial: TX 10 10 01 49 5A 16
PHY-serial: RX (fragment) E7 A7 DA
DPM1: RX error: PHY-serial: Failed to get received telegram size: Invalid telegram format.
I am using a raspberry pi as master and rs485 to rs232 transceiver and i configured my baudrate to be 45450 baud. That is the baud that DP/PA coupler support. I feel maybe my problem might be from the physical transceiver but then I saw that pyprofibus automatically reduce some devices baudrate down to 9600,19200.
anyhelp to debug this error would be appreciated.
Regards.
Hi. Thanks for your question.
The RX error probably points to a physical problem with the bus, or a baud rate mismatch.
If I remember correctly, then the Raspberry Pi serial can't physically do 45450 Baud.
I would suggest to check the physical baud rate emitted by your Raspberry with an oscilloscope.
Can you reduce the coupler's baud rate to 19200?
Hello,
Thank you for your swift reply. I really appreciate it. The pi suuports baudrate higher 45450, I have triend it with pyserial project before and it wokred fine. I think the problem might be from my transceiver. I read somewhere that raspberry pi serial supports only 3.3v but my transceiver is a TTL5v, maybe the pi is reading the data wrongly..... I am checking online on the right tranceiver to buy (for pi and for windows PC). Perhaps if you know of any or have usd any before, please i would be glad if you can suggest them to me.
The coupler only work 45450 baud as a coupler option.
to add. I am interested in the acyclic task, that would be after I get my coulpler working and read the PA device cyclically.
Regards.
Yes, the Raspberry Pi supports baud rates higher than 45450. But it doesn't support 45450 exactly.
That was at least the case last time I tested it a couple of years ago with a Pi 2.
Things might have changed since, though.
Thank you for this eye opener, I think you might be right on what you mentioned. I have tried to see if can get an oscilloscope to measure this signal baud but i cannot get any for now. seems my job for now is to be looking to find a way to work this with another device and also find an oscilloscope to read the rpi baud.
I will keep you posted once I get something.
Thank you so much for the response and tips.