OSH Park delivered early! The boards were supposed to be received from the fab and then mailed on May 11th, but I received them in the mail May 9th, gotta love that.
I assembled two by hand with a soldering iron, no solder paste, hot plate, or hot air. Despite how it looks, you can solder the microSD connector with an iron: use the window on the top of the connector to feed solder and see what you’re doing, and use a thin tip iron through the front of the connector.
I’m pretty happy with how the board turned out when used with the Photon. I used the 3.5mm high sockets from Samtec, and the pins stick out a bit through the socket, but I don’t think it’s a problem. For the Electron, I didn’t consider that the parts on the bottom of the Electron would interfere with the microSD card on the top of the APA102 shield. The inductor on the bottom of the Electron hits the shield and prevents the Electron from sitting properly. With the short sockets, I believe the pins are actually making good contact, but it’s not ideal. I don’t have a good fix for this, so the shield is unlikely to have Electron compatibility.
Quick tests are good, I can run a SmartMatrix sketch and drive the APA102 LEDs, and the Photon gets powered through the APA102 wires. I can run a SDFat library sketch and read/write to a file on a microSD card.
I added the jumper that connects VUSB and VEXT powered the board and LEDs through USB only. I ran FastLedNoise on a 16x16 matrix with brightness 64/255. The display looked fine, and a USB charger doctor showed the voltage had dropped to about 4.5V, and current draw was about 600mA peak.
I want to do a few more tests:
- Test microSD and driving the LEDs simultaneously
- Test something that taxes the power supply (e.g. flashing all white at full brightness on and off), and see how VIN looks on a scope, with and without the 10uF cap I’m still considering making DNP
- Test writing to the microSD while taxing the power supply, check the scope
- See what happens with a high current sketch on USB power - where does it break?
- Test the optional enable circuit