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RE: RS485 line turnaround




I too am interested in getting this sorted out. I recall doing
modifications myself on an 83, it was a long time ago but I think the
modification was due to a TTL logic chip not having VCC connected, I
assume this has been rectified in latest revisions.

Currently I am using tcdrain call to implement 485 turnaround, this
works but is very slow, the 83 holds the bus in transmit for around 20ms
after the last byte is gone, because this is when the call returns. I
realise there is 2 wire functionality built into the serial driver in
the kernel, but have never gone indepth enough with kernel configs to
get this working. Does anyone know what configs need to be set to get
this working, and what ioctl calls are required? This would save me lot
of time indeed. 

- Andrew Radford
Waugh Technology LTD

-----Original Message-----
From: Frank Brown [mailto:fcb3@xxxxxxx.net] 
Sent: Monday, 16 August 2004 1:37 p.m.
To: dev-etrax@xxxxxxx.com
Cc: OGurkan@xxxxxxx.com
Subject: RS485 line turnaround

Found an interesting item on my Axis-83. It is missing
D15 (D-5 on page 6 of schematic). Is this normal. Without
it, can't turn line around for RS485. It should either
have that or R72, which is noted Not_m (Not mounted??).
I jumpered pins 10 & 11, and it now works.

Thanks

Frank Brown
Phoenix Consulting
for Emerson Climate Technology
fcb3@xxxxxxx.net