Tuesday, December 22, 2009

PCBs and Testing

Few days ago I received the PCBs. Right after, I soldered all the SMD components in place and started testing the device. It took me around an hour to put all components in place, considering that I was very careful analyzing what component to solder first. You don't want to go into a grid-lock situation where one component it severely obstructing another. Here the board (top and bottom). Notice the dimensions.



The hardware is working great. No bugs in the PCB :) However, I found more bugs than I expected in my code. You never realize how easy is to forget basic stuff when you write the code. Debugging the code on PICs with small pin-count is hard if you don't have the appropriate tools. In order to run breakpoints for the 16F688 you need a special header, which of course I don't have. Fortunately, I added a debug LED (DBG white dot component, right above the black JP6 connector, to the left). The LED shares a pin with one of the programming signals, however, it works great when you need to find out what's going on.

After some hours of debugging I could temporarily connect to my cellphone and managed to dial a number. However, the Bluetooth (BT) connection constantly dropped 5-10 secs after establishing a BT connection. I monitored the 115,200 baud messages going in and out of the PIC (blue and yellow cables in the picture) but couldn't see anything abnormal. After checking that everything was setup correctly and contacting BlueGiga's tech support, I found the culprit. My cellphone doesn't support the full HFP profile. It is a three years 'old' (!) Samsung SCH-A870 phone and has an outdated HFP profile (v.1.0). The current HFP profile is v1.5 and apparently don't work together.

I tried another phone (LG enV2) and voila! It works flawlessly! I get dial tone when BT is connected (busy tone when not), can make phone calls, rings when receiving them, even dial a phone number using voice recognition (flash feature I added). It works great!

Next stop: get another cellphone and do some more testings before packing in into the Ericofon.

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