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akidder
1519 Posts |
 Posted - 04 Mar 2002 : 18:28:20
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Q: I tested the voltages on Graphics Master serial ports A and B and all the pins read 0V.
Q: Bitsy Serial Port 1 works normally except when I connect a loopback cable.
The low-power RS-232 drivers for Graphics Master Serial A & B and Bitsy Serial 1 power down when not connected to another RS-232 device. They power up when a valid RS-232 level is detected on any of the input lines (RX, CTS, DSR or RI).
This is typically only important if:
1. You are testing voltages on a cable (open-circuit),
2. you have connected a passive loopback to the serial port or
3. the device you are connecting to has a similar power management scheme.
In the latter two cases, the system(s) will be in a deadlock condition in which neither turns on. One solution is to pull up an unused line to 3.3 or 5V to enable the buffers. ADS also has an alternate part it can populate on production systems to disable this feature.
Drew Kidder
ADS Technology Transfer
Edited by akidder 25-Mar-2003: Update to include notes about Bitsy Serial 1 and loopback issues.
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robertbowen
10 Posts |
Posted - 09 Feb 2003 : 15:39:51
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Forum -
I am unable to use Serial Ports A & B on my Graphics Master as well.
My Observation:
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I'm using the Terminal Program in CE. I have connected my Fluke meter to Serial Port A and/or B and I am unable to communicate with the Fluke Meter. The same test on COM Ports 1-3 work fine reading/ communicating with the Fluke meter.
Testing Serial Ports A & B
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Following the instructions describe here under "Testing that the PC serial Ports works(loopback)" also prove to be unsucessful. I have shorted pins 2 & 3 on the DB-9 connector, opened the Terminal program, and no characters are echoed back.
Performing this test on COM 1-3 prove to be sucessful.
Hardware connection
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I have a ribbon cable on J20. I have wired a DB9 Male connector for both Serial Ports A & B as followed?
Serial A
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J29 -> Pin 23 ---> Pin 2 on DB9 Male connector
J29 -> Pin 25 ---> Pin 3 on DB9 Male connector
J29 -> Pin 27 ---> Pin 8 on DB9 Male connector
J29 -> Pin 29 ---> Pin 7 on DB9 Male connector
Pin 1,4,6 on DB9 Male connector Shorted
J29 -> Pin 37 ---> N/C
J29 -> Pin 39 ---> Pin 5 on DB9 Male connector
Serial B
========
J29 -> Pin 24 ---> Pin 2 on DB9 Male connector
J29 -> Pin 26 ---> Pin 3 on DB9 Male connector
J29 -> Pin 28 ---> Pin 8 on DB9 Male connector
J29 -> Pin 30 ---> Pin 7 on DB9 Male connector
Pin 1,4,6 on DB9 Male connector Shorted
J29 -> Pin 38 ---> N/C
J29 -> Pin 40 ---> Pin 5 on DB9 Male connector
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Perhaps I have to enable these ports in a *.REG files or something? I'm open for suggestions/comments?
Kind Regards,
Robert
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akidder
1519 Posts |
Posted - 11 Feb 2003 : 18:52:22
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Issue Resolution:
We resolved this issue offline. The Fluke meter probably has the same type of power-saving serial buffers as on the Graphics Master, creating the "deadlock" condition described in the original post.
There are a couple ways to test and work around this issue:- Test the connection with a desktop PC.
Desktop PCs don't typically use power-saving serial buffers, so should activate the Graphics Master buffers.
- Force the Buffers On
You can force the serial transmitters on by connecting J20.48 (RTS D) to J20.37 (RI A) and/or J20.38 (RI B). This will enable the transmitters for Serial A and B.
- Change the Buffers
If this feature will cause problems in your application, in production we can install buffers that do not have this feature.
Drew Kidder
ADS Technology Transfer
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No voltage on Serial A or B (GMaster) & Bitsy COM1
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