LK204-25 Can I use RS232?

awasilenko · Post by **awasilenko** » Sun Aug 05, 2007 9:35 am

I originally bought a Matrix LCD from parallax for my STAMP chip, but I have since lost interest in STAMP but I still want to use the display. I just placed an order for a USB to RS232 adapter because my laptop does not have a port, but then I read in the extra PDF provided by Parallax, this model might not have RS232 because it was specially designed for stamp's TTL serial. I hope this is not the case, but I need confirmation either way so I can figure out my options, I really don't want to buy ANOTHER adapter for usb to TTL. Can I just solder on a db 9 connector on the blank pins and change a jumper or something?

http://www.parallax.com/dl/docs/prod/au ... a-V1.2.pdf

Raquel · Post by **Raquel** » Tue Aug 07, 2007 10:46 am

Hello awasilenko,

Thanks for your post.

I recommend that you use PCB Rev 2.0 in case you are starting a new design for a project.

With PCB Rev 1.23, unfortunately putting these boards to TTL (as with STAMP) entailed cutting of traces, which you will have to re-connect to go back to RS232. A couple of jumps will have to be unsoldered and yes, you will need to put a DB9 connector (this would require to take the white connector out).

With the link you gave in Parallax (picture) you can see the cut traces under the SIPEX IC, and the solder pads to the right of the IC.

I hope this helps.

awasilenko · Post by **awasilenko** » Tue Aug 07, 2007 1:35 pm

Well this isn't all bad news, at least it is possible. Unfortunately I am stuck with Rev 1.23. So let me just confirm everything that needs to be done:

1. Remove white connector and attach DB9
2. Reconnect the two traces under SIPEC IC
3. Attach unknown sized resistor to the 4th pad directly under the SIPEC IC

Any other steps?

Also is that really a connector between the two boards? Last time I tried to separate the boards it appeared the pins were soldered right threw the connector to the other side, it wouldn't budge at all, then again I wasn't trying too hard. I will have to try again to solder the DB9 onto the board eventually...

Is there an option of me sending this LCD in to you guys for this to be done, or perhaps you can sell me a v2.0 board to swap with the 1.23?

Raquel · Post by **Raquel** » Tue Aug 07, 2007 1:46 pm

Hello,

Yes to both 1 and 2.
I am not sure what you meant for 3.
But the other thing was the solder pads that were soldered / bridged. Compare these pads to the ones on page 7 of the manual.

awasilenko · Post by **awasilenko** » Tue Aug 07, 2007 2:10 pm

What I ment for 3 was, I know I have to solder a resistor into the blank spot, but I do not know what size of one to put there. It was a kind of a "fill in the blank" statement.

I see the two pads that needs to be cleared.

Any comments/tips for unsandwiching the two boards?

Raquel · Post by **Raquel** » Tue Aug 07, 2007 2:19 pm

Sorry, I still am not sure of what you mean. I have not mentioned anything about the 4th pad directly under the SIPEX IC, so I am still not sure

As per clearing the solder blobs, just simply wicking the solder out is good.

awasilenko · Post by **awasilenko** » Tue Aug 07, 2007 2:35 pm

Hey your right, I must be loosing it

.

I will operate on my board in a few days and let you know how it goes, I am still waiting for my USB to RS232 adapter to come in so I can't test it yet. I got to find a DB9 connector too, I may get lazy and just solder some wires to the pins I need.

awasilenko · Post by **awasilenko** » Sun Aug 12, 2007 2:56 pm

Well I got the adapter and did what you said, and to my suprise it worked!

Incase anyone cares what I did with it: