Mesa 7c80 Smart Serial

Has anybody used the Smart Serial port on a 7c80? I'm trying to create a touch screen pendent using the LBP protocol on a stm32F432 at the moment I'm just trying to get this basic example github.com/fdarling/mesa-smartserial-device-template.git

when I load hm2_rpspi the stm32 receives 0xDF 0x16 to which it responds with 0x5A 0xA5, but this cycle just repeats for a few iterations but nothing else happens.

It's like the response isn't being received but I've hooked the TX line from the stm32 to a RS-232 port on a PC and it is indeed transmitting the correct responses.

Can anyone confirm they have successfully used the RS-422 port on the 7c80.

Failing that I guess I'm going to have to order a 7i73 to test it myself, I don't mind doing that but really I would like to make some progress this weekend rather than wait a week for another delivery.

Thanks
Russell

I've had our test 7C80 running with a sserial remote for a while so I don't think
this is a 7C80 issue. Marginal 2.5 M baud rate maybe?

Thanks, that did occur to me, but I've tried much lower baud rates and I get the exact same result with every rate I have tried except for 115200 but that is a special case in the linuxcnc code.

Is there an easy way to the access the uart on the 7c80 outside of the hostmot driver to verify physical connectivity in both directions?

Not really as the UART connects to a embedded CPU on the FPGA that runs the SSLBP
protocol.

It looks like the 7C80 is not seeing any response, is it possible you have the RX lines swapped?

I've also tried swapping the RX+ and RX- lines over but it makes no difference.
The only nagging doubt I have is that the stm32k432 board is a 3.3v device and the RS-422 transceiver i'm currently using has a MAX490 chip on it which Is a 5v ttl device. if I connect one of the pairs to an RS-232 to USB adapter I do get out the expected data, but I can't tell if the other half of the pair is correct. I do have some loose Maxim 3490 chips so I think my next move is to solder one to a soic to dip adapter and see if it makes any difference,

Yeah, I just retried a 7C80 and it seems OK with sserial devices



Sounds like the 7C80 is just not receiving the data somehow

Thanks for checking.
I've just swapped out the transceiver and that got me a bit further in that hostmot2 found the device but reported timeout errors during the discovery phase. I managed to remove those by disabling the output that the stm32 was writing to the other serial port.

I suspect I'm going to have to ditch the Arduino framework and get a bit closer to the metal to get this working reliably, but at least I know the hardware works now.

Thanks again for you help.

Regards
Russell

Yes, you need close to real time response from a sserial remote.
What's more, the interface is generous during setup and discovery
(1 ms timeout) but during process data transfers it only allows the
nominal (measured) response time + 20 usec or it times out the transaction