Here is a mostly assembled HAC-1 board:
What has happened so far:
- Soldering of 208-QFP CPU chip, TSOP DRAM chip on backside. For IC mounting, a soldering iron temperature of 300C was used. One of three attempts at the CPU mounting was a failure due to pins getting bent when appying too much heat trying to wick away excess solder. Next time, 280C might work better.
- Add 5V and 3.3V regulators, connector for FTDI Chip TTL232R cable.
- 1st attempt at communicating with CPU. At the time, we hadn't ordered our surface mount resistors and caps, so we wanted to try verifying CPU operation without the passives. We tried connecting using the Flash Magic tool (unfortunately Windows-only, but it looks like it should work with little trouble in WINE under Linux), and sent an "Erase Flash" command. The CPU did not respond.
Here's where a little bit of sloppiness on our part comes in (lessons learned.. for the nth time). Our first idea was to check the oscillator so we probed that with the scope, and were discouraged when we saw no signal on the oscillator circuit. However, according to the LPC 2478 User Manual, the chip contains a 4MHZ internal RC oscillator which is automatically used on startup. The external oscillator circuit does not start up until it is told to do so in software.
After obtaining and mounting the passives (all 0805 size, soldered at 280C), the CPU did indeed respond to the Flash Magic erase command! My suspicion is now that the lack of the pull-up resistor on the reset line may have been the cause of failure before. My assumption was that unconnected lines should tend to float "high," but I guess this is not necessarily the case.
The plan now:
- UPDATED: Precompiled binaries from gnuarm.com did not seem to work. Will have to build from source. Not too hard to do, though.
- Write and test simple standalone CPU code: LED blink, serial port, external memory test, LCD driver.
- Add SD card interface, figure out how to configure U-boot or some other bootloader for ucLinux. Linux image should be stored on SD card.