I’ve finally gotten around to assembling my first prototype. I’ve had the board and components in my hands for a couple weeks, but have been kept pretty busy with schoolwork and senior design. This post documents the process I took bringing up the board.
Preliminary inspection of the board didn’t reveal any major problems. There are no visible faults and no shorts were detected. This is very good as there was a mix-up at the board house, and I received two prototype boards instead of one!
The voltage regulator was brought up first. Unfortunately, this was also where I spotted my first board mistake. The footprint for the DC Jack was generated upside-down. This was a manageable fault, however, as the main connector pins are in a line. Bending the third terminal out of the way allowed the connector to be seated. A 12V supply was used to fire up the regulator, which worked perfectly as indicated by the LED and measurement with a multi-meter.
Next, the USB section of the board was built, I encountered another footprint error with the USB connector in this section. However, the footprint was close enough that the connector still fit after some minor coercion. If this experience has taught me anything it’s that you should always purchase your components before you send the board out for fabrication. I’ve already bought myself a set of calipers to, to ensure I never make this mistake again. Aside from the connector issue, the USB subsection seemed to supply power just fine.
The micro-controller section followed and everything here went according to plan. Loading the boot-loader went smoothly as well. I’m really glad I bought an AVR programmer, it has really made things easy compared to hacking together a programmer every time I need one.
Finally, the rest of the components were installed. This included the reset circuitry, audio processing, and graphic EQ sections. Everything here installed fine, all of the remaining footprints were correct. One design error was detected; according to the FT232 datasheet, the test pin (26) needs to be grounded. I missed this the first time through and couldn’t talk to the Atmega’s bootloader until a shorted pins 26 and 25.
As of all low voltage sections are complete and I’ve successfully loaded some test programs onto the microcontroller. I’ve got plans to develop libraries for the peripherals and make sure everything is running smoothly before I populate the high voltage section of the board.