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 How do I use RS-422? [AGX]
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sadev1

3 Posts

Posted - 04 Jun 2004 :  14:44:11  Show Profile  Email Poster
I am trying to enable RS-422 for use on our AGX board. (AGX Windows CE Ver.(4.20.02)) We have JP10-13 set to pins 1,2 as shown in the manual, and have a 3rd DB-9 connector connected to lines 22,24,26,28 of J14 on our Serial Adapter cable as shown in the manual.

None of the lines are carrying any signals. What are we doing wrong?

ccoats

18 Posts

Posted - 03 Aug 2004 :  14:48:23  Show Profile  Email Poster
We have VGX boards (similar to AGX) and are having similar problems. When I look at the transmit lines with an o'scope I see nothing. Has anyone used the 422 on the VGX / AGX?

Edited by - ccoats on 03 Aug 2004 17:39:01
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sadev1

3 Posts

Posted - 04 Aug 2004 :  12:24:19  Show Profile  Email Poster
Yes, I got ours working.

On the AGX(and probably on your VGX), RS485/422 are on the same lines. So, I tried getting 485 to work, and put these lines into our ADSLOAD.reg:

[HKEY_LOCAL_MACHINE\Drivers\BuiltIn\Serial]
"RS485"=dword:1

Lucky for us, this enabled both 422 and 485 on our AGX.
Hopefully it will work on your VGX as well.

Good luck!

Edited by - sadev1 on 04 Aug 2004 12:32:41
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rwhaley

628 Posts

Posted - 05 Aug 2004 :  15:33:55  Show Profile  Email Poster
#Linux_422_485

For Linux systems there are two things to do to make RS485/422 work:

1. To enable the receiver:

echo 1 > /proc/sys/ads_misc/rs485_receiver_enable

2. To enable the transmitter, set RTS:

ioctl(ttyfd, TIOCMGET, &status_out);
status_out &= ~TIOCM_RTS;
ioctl(ttyfd, TIOCMSET, &status_out);

When more than one device will be sending data RTS should be turned on only when writing. RTS should be turned off when not sending so the other devices can transmit.

If no other devices will be sending data then RTS can be left on all the time.
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SGV3000

4 Posts

Posted - 27 Jul 2005 :  14:00:07  Show Profile  Email Poster
I am using a VGX with Windows CE 4.20.23, and the trick of setting the RS485 registry setting has NOT helped me to overcome the same issue of TX+ and TX- pins (J14:26 and J14:28) both staying low. I am trying to use COM1 for full duplex RS422, so I have JP6 and JP7 not installed and JP10-JP13 connecting 1 and 2. I tried adding the registry settings:

[HKEY_LOCAL_MACHINE\Drivers\BuiltIn\Serial1]
"RS485"=dword:1
[HKEY_LOCAL_MACHINE\Drivers\BuiltIn\Serial]
"RS485"=dword:1

but it didn't change anything.

Does anyone have any other suggestions?
Thanks.
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hchin

30 Posts

Posted - 27 Jul 2005 :  17:27:15  Show Profile  Email Poster
Try using the newer key instead. So replace the old key with the following in your adsload.reg. The example below is set for RS422.

[HKEY_LOCAL_MACHINE\Drivers\BuiltIn\Serial]
"SerialMode"=dword:2 ;0=use RS232, 1=use RS485, 2=use RS422
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