logomatic logic conversion

Everything ARM and LPC

Moderator: phalanx

Post Reply
fsalas10
Posts: 12
Joined: Mon May 18, 2015 2:42 pm

logomatic logic conversion

Post by fsalas10 » Wed May 27, 2015 8:32 am

Hello all,

I am hoping that there is somebody out there who can help me with logic conversion. I am using a logomatic serial data logger. I have a basic two transistor logic level converter from the computer to the board. My issue is that when I log data in mode 0, I get back garbage. The garbage is consistent, but still garbage. The baud rates, parity, stop bits, etc. match. I have used an INTRONIX Logicport to see what is happening before and after logic level conversion. According to the logic analyzer, everything works fine, but what I get on the sd card in the logger tells a different story. So, I am just wondering if anybody has had similar issues.

Thank you,
Frank

fsalas10
Posts: 12
Joined: Mon May 18, 2015 2:42 pm

Re: logomatic logic conversion

Post by fsalas10 » Wed May 27, 2015 10:17 am

In case anyone is having similar issues, I am posting my "progress". Well, I said forget about the logic analyzer and I instead opted to just plug the short the tx to the rx line coming from the computer. I did this in several spots along the circuit and I found a few problems. First of all, I was using a 3906 and 3904 transistors. I switched for a quad2 and 2907. This helped. Also, I don't think that I was fully turning on the quad2, so I lowered the resistor feeding the base. This also helped. Now, the rx line receives the ascii as it should before and after the quad 2, but the logomatic still gets garbage. I am trying to understand why the shorted tx an rx get the same characters, the logic analyzer gets the same characters, but the logomatic doesn't. I have checked and rechecked the LOGCON.txt file, and all of the setting with RealTerm. I will keep cracking away at it, but help would be much appreciated.
Thank you

jremington
Support Volunteer
Posts: 2102
Joined: Fri Jun 15, 2007 9:41 pm
Location: Eugene, Or

Re: logomatic logic conversion

Post by jremington » Wed May 27, 2015 11:27 am

Unless you post a circuit diagram, no one will have a clue what you are talking about.

fsalas10
Posts: 12
Joined: Mon May 18, 2015 2:42 pm

Re: logomatic logic conversion

Post by fsalas10 » Wed May 27, 2015 1:00 pm

jremington wrote:Unless you post a circuit diagram, no one will have a clue what you are talking about.
You are right. Here is the URL of the circuit that I hijacked https://www.sparkfun.com/tutorials/215. I figured out my problem though. I connected that cap to the GND of the PNP, and I took out the 10k that was connected from the cap to RX-RS232. I am a newbie at this stuff, I am still in school with one more year left for a EE degree, so have some pity for my silly antics. They don't teach troubleshooting in school haha. Now I need to do something I hate and look at the code to make it do what I really want.

Post Reply