This time, a post without pictures; I'm on the road now and left my camera at home. Why write a post then? Well, I'm very excited to tell you all that I managed to create a wireless connection with my own hardware for the receiver! Soldering the IC was a bit of a challenge, and I'll post a video on how that went later on. After that, I soldered all other components. The largest excitement came when I placed my coil on the demo board transmitter... and got a flash of green on the status LED after which it became a bright red...
Red, that's a good color for 'error'. The manual said something about the temperature sensing at JP1 of the transmitter board, but since the original receiver worked fine I was quite certain that the error was on my receiver. I took a good look at the demo receiver schematics, and at my own design and detected the *cough* quite dumb *cough* mistake; I had made some weird resistive divider between FOD (can anyone tell me what that abbreviation means?) and the TS_CTRL pin. As far as I recall I did that for the temperature sensing, but I really cannot find how I came to this error. The right connection is different, as I will write below:
Update to those who used my design for the BeagleBone Qi cape as a starting point
Now that I have a working receiver circuit I can also tell you what I found out I had misdesigned; I will update the schematic in the next week, but I can already give some info:
- Some component values / ordering codes are wrong. At least, the list I sent to Farnell had some errors in it; the ordering code for the 68nF capacitors gave me 6.8nF capacitors, and I forgot to order 10nF capacitors; I'm not sure the same errors are present in the first design, but please be aware of this when ordering / making a bill of materials. The values in the schematic are correct.
- The FOD pin should be connected to GND via a 140 Ohm resistor
- The TS_CTRL should be connected to GND via a 10kOhm resistor
OK, more updates will be coming (a revised schematic for instance), stay tuned!