Experimental Physics and
Industrial Control System

From: Tech-talk <tech-talk-bounces at aps.anl.gov> On Behalf Of Mrinal Bera via Tech-talk
Sent: Monday, October 30, 2023 1:32 PM
To: tech-talk at aps.anl.gov
Subject: Cannot do successful RS-232 communication with baud rates <2400 with VME and IP module

Hello,
While configuring RS-232 communication through XM-octal breakout boards with TVME-200 (with IP-Octal serial module) and MVME3100 using EPICS 7.0 and vxWorks-6.9.4, I did some quick tests with asynRecord. I found the following:
1) With loopback communication(when I sorted the 2 and 3 terminals of the RS-232 ports) with the baud rates of 2400 and above, I received the same input and output values (as shown in the 1st attached image). That shows that RS-232 communication is OK.
2) With the baud rate of 1200, the Output and Input values of asyRecord are different (as shown in the 2nd attached image). I suspect either the tyGSModule or TVME-200 with IP-Octal Serial board has some issue with communication baud rates below 2400.

When I checked the IP-Octal Serial module documentation I found the baud rate information as ‘Programmable in 18 steps to 34.8kbps’. I dug further into the information regarding the baud rate of the chip used in the module (i.e SCC2698B). I found that the chip supports 26 fixed baud rates from 50 to 38.4kbps. Hence, I think 1200 kbps should be supported by the chip and IP-Octal Serial module.


I need the baud rate of 1200kbps to interface the Lakeshore 330 temperature controller with EPICS on VME hardware. Did anybody try to interface Lakeshore 330 with VME and IP modules?


Best regards,
Mrinal