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Asked — Edited

Ps2 Cable For Roomba

I just want to double check something on the PS2 cable for Roomba connection.

As I understand I need to connect to pin 3 (RXD input) and Pin 7 (ground) Your tutorials say to make sure there is no voltage or I will fry the D0 port.

So here is what I don't understand:

Pin 7 is supposed to be ground and when I connect the multimeter to pin 7 and pin 3 it shows no voltage. However, if I touch one lead of the voltmeter to the grounded base of the serial port (the outer barrel) and the other lead to pin three, I read 4.5 volts. Obviously there is voltage to pin three, but only when it is grounded to the port's barrel and not when I am connected to pin 7 as ground.

Also, pins 1 & 2 read between 12 and 14 volts when I connect the multimeter to those pins and the base of the port, yet when I connect the meter to pin 1 or 2 and the negative lead to pin seven, that voltage drops to 7.5 volts??

I suppose that I should just trust the meter that shows zero voltage when connected to pins 3 & 7, but What exactly is pin seven doing? Why does it show voltage when the multimeter is touching the grounded base and not when it is touching pin 7 ground?

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#1  
Be very careful. I bought some cables from China. I stood there for hours trying to get it to work. I went through three bad cables and the fourth one worked. I put my wires on 2 and 6. Of course I had a six pin just like in the video. It you are working with a seven pin connector, I believe 3 and 7 are the correct pins. But, NO voltage.

Good Luck!
:D
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Synthiam
#2  
I have on my list to do a better video and photo diagram. i'll do it tomorrow, i promise:)
#3  
Sorry, moved this more appropriately to the Hardware section.
#4  
If I were you, I would wait for D.J. s next video. He promises to make it clear. It should be posted in another couple to three days. Maybe even as early as today or tonight. Be patient and you won't burn up your board.

Me, not being patient, burned up three Roomba motherboards. I had a Factory cable from I-robot and every unit I plugged it in to burned up the communication port making it useless for robotics unless you replace the motherboard.

But, in the end, I built another cable and salvaged what I had left.
#7  
Okay, thanks DJ! I noticed that I was looking at the pins in reverse (part of the problem), but I also discovered that the PS2 cable I was using had 6 pins but only 5 wires and wouldn't you know the one pin that was not connected to a wire was pin 7!

I dug up an 8 pin cable from an old serial modem that might work. The only problem with this one is that the ground wire connects to both pin 7 AND pin 8 in the very centre of the plug, but that one just sits in a dead rectangular hole in the roomba serial port,so it should be okay, right?
#8  
Sorry, moved this more appropriately to the Hardware section.
#9  
Most Roomba questions can be found at Roombareview, do a google search. I am not too sure of the location. As far as the EZ-robot Board , D.J. is the man.

All I remember, and don't hold me responsible, it is just food for thought:

On a 7 pin connector 3 signal, 7 ground.
On a 6 pin connector 2 Signal, 6 ground.

Make sure you orient the plug correctly , or you will burn up both the Roomba AND the EZB.

The 540 Model is an EXCELLENT Heavy Duty model.

Mel