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RJ9 Cable (4 pin) to RS 232 Cable (9 pin)

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simply_me

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Hello,

I'm attempting to connect a device (syringe pump) to my computer. The device itself is pretty old, so the original cable was lost at some point. I've tried looking for a new cable but with no success. I've also tried to search the web (for ~3 hours) to find an adapter or a schematics of such an adapter, so now I decided to do the adapter myself (with your generous and much appreciated help:). Where do you recommend me to start the design stage? Any thoughts on the matter?

In general, the device address is set to 0 and the baud rate can be-- 300, 1200, 2400, 4800, or 9600.
Attached the pin out of the RJ 9 of the syringe pump and the standard pin out of RS 232.

Thank you,

Simply
 

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Last edited:
On the Computer connector:

Pin 5 Sig GND goes to your Sig GND.
Pin 2 Receive goes to your transmit
Pin 3 Transmit goes to your receive

That should work. Worst case if I screwed up reverse pins 2 and 3.

What software do you plan to use to communicate with the pump?

Ron
 
Hi Ron,

Thank you for your reply, I don't mean to doubt the pin out above, but are you sure I don't need to have a buffer as the serial port needs to get signals to receive/transmit? Just a thought. I plan to use LabVIEW to communicate with the pump, I'll pass command strings to it....
 
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On your pump pinout they only use 3 lines. Ground, Transmit and Receive. So from your RS232 DB9 Pin 5 is Ground and goes to Ground, Pin 2 is Receive and goes to Transmit and Pin 3 is Transmit and goes to Receive. So that is how the RJ9 on the pump should mate with the RS232 of the computer. I would have suggested Hyper Terminal but since you have Lab View that should work. While not familiar with your pump that is how I do it to communicate with devices.

Ron
 
Let me know as it should work.

Ron
 
Hi Ron,

I've tried the setup, connecting data in to pin 2 and pin 3 (tried both ways), and something odd happens. The syringe pump shows that it's connected but when I try to use Hyper terminal or Labview I get a run time error (device doesn't respond). Any suggestions on how to proceed?
 
Well it looks like you have communication. The error sounds like what it says. I don't know what the pump should be sending. This stuff is far from my forte too. :) Are you choosing the correct comm port?

Ron
 
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