Here it is, the latest rev of my low cost PICAXE board for kids! Same size, but more pins than before! When I make these in large quantities, the cost of putting components on the bottom side of the PCB is negligible, so I decided to do just that and cram in a larger PICAXE.
I was very excited to get this board soldered, so I assembled one at work, only to find that it didn't work. When I plugged it in, the power LED came on, but I didn't get my friendly Windows chime that it makes when USB devices are recognized. Thinking that maybe I did a bad job, I soldered up another one. That one also didn't work! No way, I couldn't have made a mistake on the schematic, could I? I mean, it was just a PICAXE change, a different LDO, and I added a jumper for external power.
I brought the boards home with me, hoping that I would find time tonight to diagnose the problem. Luckily, I did find the time. And there were a lot of problems.
The first thing I did was take a bare board and check the connections. I found that there was a trace in my layout that shouldn't have been there. I think that in the process of routing and rerouting, I forgot to delete an extra trace and ended up with some components shorted to ground. Next, there was a trace missing between the CH340G and one of the 22pF capacitors.
Once I made these changes, the COM port was recognized! Yay! Ok, now to test my simple program from the 14M2 on the 20M2.
But it wouldn't program. The first thing I checked was the Serial In line, and sure enough I found a problem there. One cut and add later, I got it all working. Phew.
I'm not sure that video uploaded properly. You can also see it on Google+.
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