Hello,
We are using Vulcan board with Arcom Embedded Linux. The RS485/RS422 port is configured for RS422. Our application using the RS422 port works fine with Vuclan Rev.A or B, but failed with Rev.C. Eurotech forwarded us the following information on the changes between Rev.B and Rev.C:
“Mod to add Auto485 function.
a) Replace U18 2460-50345-000-000 with EXAR XR68M752 2460-52894-000-000.
b) Lift U6/pin2 off the board and short U6 pad 1 and pad 2 on the board (leaving pin 1 attached).”
After investigation, we see that:
On Vulcan Rev.A and B:
- U6 (LVC14A) inverts the RTS signal between U18 UART (XR16L2551) channel B and U28 transceiver (SP3491).
- Our application opens a serial port (ttyS3) in 'raw' mode without flow control.
- Arcom Embedded Linux forces RTS to low. So, when inverted the transmission is enabled on U28.
On Vulcan Rev.C:
- As documented by Eurotech, U6 seems to be bypassed on Vuclan Rev.C. Then, RTS is not inverted any more.
- Arcom Embedded Linux continues to force RTS to low. Then, the transmission is disabled on U28.
We are able to force RTS by the application using ioctrl TIOCMGET and TIOCMSET. However, we want to have only one application version working for every Vuclan board revision. Our questions are as follows:
1) Do we have a good understanding of the modifications between Rev. A/B and C?
2) Where can we find the Vuclan schematics of these sections? Are the schematics available?
3) Why the RTS is inverted in Rev.A/B and not in Rev.C?
4) How to make our application working on every revision?
5) How to configure the RS485/422 port on the Vulcan using Linux API?
Note: the last Arcom Embedded Linux package that we received is version 4i4.
We do appreciate your assistance and prompt reply.
Regards,
Jean-Sebastien |
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Port RS422 not working on Vulcan Rev.C
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Posted - 17 Sep 2010 : 10:58:34
