DOH! I guess I accidentally bumped the power line before autorouting. I fixed that problem with a simple add, only to run into another one -- the app couldn't program the PICAXE. However, the programming tool could correctly detect the type of chip connected, as well as its firmware version. What an interesting paradox. I inspected the TX signal and found that processor was sending periodic data packets. Each packet looked like it coincided perfectly with the timing of the processor detection on the application side. I probed the RX signal and saw that there was no activity when I tried to program the processor. In fact, the RX line was always high, and a high state is what tells the PICAXE to report its processor information, and that's why the application was able to tell what was connected.
I found it very unlikely that one input of the inverter was bad, but I replaced that chip anyway. It didn't solve the problem. I also changed the PICAXE for another one, but it behaved the same way. something on the board is causing the RX line to be pulled high.
I found it very unlikely that one input of the inverter was bad, but I replaced that chip anyway. It didn't solve the problem. I also changed the PICAXE for another one, but it behaved the same way. something on the board is causing the RX line to be pulled high.
I soldered up a new board section by section, thinking that if it's a design issue, I would see the problem on another board. I started with the LDO and inverter chips, and they behaved as expected. I then added the serial converter and its related components. All good. Finally, I installed the PICAXE and voila, it worked!
I had one board left so I soldered that one. It was also good.
I need to go back to the bad board to try to determine the cause of the problem. I don't think it's the serial converter chip because it's on the opposite side of the inverter. The output of the inverter is somehow pulled high. At this point, I think I will start removing components one by one until I can isolate the problem. I know that when I installed the inverter on this board, I had trouble soldering the SOT363 package and had some large bridges to clean up. The solder wick was really thick and I used a lot of heat to remove the solder. Perhaps I damaged the board...
Next up, I think I'll post some videos of bringing up the board and doing a simple breadboard project.
I need to go back to the bad board to try to determine the cause of the problem. I don't think it's the serial converter chip because it's on the opposite side of the inverter. The output of the inverter is somehow pulled high. At this point, I think I will start removing components one by one until I can isolate the problem. I know that when I installed the inverter on this board, I had trouble soldering the SOT363 package and had some large bridges to clean up. The solder wick was really thick and I used a lot of heat to remove the solder. Perhaps I damaged the board...
Next up, I think I'll post some videos of bringing up the board and doing a simple breadboard project.
