Today, after 13 days of shipping time, the PCB’s for this project arrived. They look good and I have no complaints about the quality of the boards. I think YOUPCB.COM did a great job on these boards and I would use them again for small quantities. The only issue I had was in the tracking number. I had selected DHL as the carrier and when the PCB’s shipped, I was sent an email with a “tracking number” contained within. It was a tracking number per-sea but not one that I could use with DHL’s tracking system. I have no idea what number to use and thus far, no one at YOUPCB support has been able to give me a valid tracking number.
After putting out a few fires today, I was finally able to sit down and populate the PCB with some parts. The only SMT part on the board is the USB mini-B connector, which I hand soldered rather than breaking out the reflow-oven. After soldering all sockets and passive components, I decided to insert the USB-to-serial module to check for proper power supply. I did not solder the module to the board and am glad I did not because I noticed that the power rails were reversed. Upon reviewing the PCB footprint to the schematic, I realized that I had reverse the pin numbers for the USB connector pads on the footprint. I reworked that issue thinking that was the fix and inserted the 8052, RAM, ‘573 latch and GAL20V8. Upon applying power, the blue power indicator on the USB-to-serial module illuminated for a moment then went dark. I removed the IC’s and checked the supply rails only to find they were still reversed. I went back to the schematic and footprint and found that the 5 I/O pins on the module’s footprint were also reversed. Luckily, I had managed to reverse the pins on all the used connections, which meant that I had actually mirrored the module. Nice save! I simply re-soldered the BERG-STIK pins to the components side of the module and flipped it over. It is possible that was my intention from the beginning. As can be seen in the photo, the module fits fine. In fact, the module has a very bright blue LED on it. Flipping the module over actually keeps one from being blinded by the light emitted from the LED and the light from the blue LED can still be seen.
I did find a crowding problem with the ISP and port-I/O pin connectors. I also thought I had some extra right-angle tactile switches, which the PCB is laid our for, but found I had none. For the time being, I used a horizontal tactile switch with two pins cut off.
I have not fully tested the 8052SBC because I am awaiting some 28C64 EEPROM’s and the ATMEL AT89S52’s. Although the PCB is laid out for use with a 28C64, I can probably use the 28C256’s that I have around. I know that the upper two address bits (A14/A13) need connection and I could have used a jumper on pin 1 to select between the “BUSY” and A14 signals but I really wasn’t planning for that. I hope to get the 8052 BASIC V1.4 assembled, burned into the 28C64 (when it arrives) and have a functional PCB.