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Comet64 Backward Compatibility Test: PASS

Posted on July 5, 2012 in Category: Blog - 0 Comments

Comet64 Compatibility Test

Hooked up the Wiz100SR - the module I used in the Comet64 - to see if the ATMega chip could access it and to make sure that it connected to the Internet in the same way as the Comet64. The test passed.

Hold on there - it wasn't THAT easy, of course... there's always something to go wrong and here's what did go wrong: After soldering it up, I was unable to see the Wiz100SR with the Wiz Config Utility - the LINK LED was working and I saw the ACTIVITY LED blink a few times, but it was dim. Didn't think anything of it at the time. I then tried the module back on a standard Comet64 and saw that the configuration was all screwy. Something changed it.

Later, I uploaded my "Blink LED Test Program" which worked fine until I put the Wiz100SR back in there. I also noticed the power LED was dimmer than usual. This led me to believe that there was some sort of power problem.

Good thing for Thursday night Commodore fun - Agent Friday came over and we did some troubleshooting. First, I tried replacing the capacitors (I wasn't super happy about the soldering job so I thought there could've been an issue with that). Same problem. Next, we decided to plug in only one side (the ethernet side) of the module, leaving the other side dangling. Same thing. A-ha! Now we're getting somewhere. So we started removing the pins on one of the risers, one at a time until the blinking LED program worked. It was the first pin I tried. So I got to thinking... let's try another power source, so we hooked up a different adapter that goes through my breadboard, which is all power regulated to 3.5 volts. It worked!

We then looked at the wall wart (which is one of those universal adapters)... the power was set at 3v - not nearly enough to power all the devices on the board. So I bumped it up to the next choice: 4.5v and that provided enough juice for it to work. Whew! One nice thing about all this is that I discovered the voltage regulator I'm using has a giant voltage drop of 2.2 volts at 350ma (!!), which is partially to blame. I'll now be doing some research on a better regulator.

Now I'm wondering if this power problem is related to the MISO problem I posted earlier... on to the next test!

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