After debugging a design for a good two hours late last night, the problem was found at the photo sensors (seeedstudio.com/depot/photo- … ml?cPath=6).
Turns out the ones I got have different pin-out than what the data sheet describes… Also, the drawings in the data sheet don’t quite match the actual physical design of the component - is the datasheet really for this product?
Anyway, in case more people experience this, try the following pin-out (which is what is used on the device I got):
Seen from top (looking down at diode/phototransistor), with notch on lower left of device:
Upper left: diode’s anode
Lower left: diode’s cathode
Upper right: phototransistor’s collector
Lower right: phototransistor’s emitter
Any more info from Seeed on this topic?