May 282017
 

So… after some cursing at me being dimwitted enough to get the amplifier around the wrong way… and luckily the amplifier is a tough little beast… I managed to get some basic functions going.

It is supposed to be polyphonic, the synthesizer supports it, and it does actually work, but it seems my GPIO arrangement isn’t picking up multiple buttons correctly.

Ahh well, we’ll get there. 🙂 At least it is making noises and flashing lights on cue, so in that sense, a minimum viable product has been achieved.

Ohh, and I was able to bump the sample rate to 16kHz. 32kHz was a bit much for the little MCU though, it couldn’t quite keep up.

Code size at this point is 3.6kB… so still lots of room left. The answer might be to implement an I²C slave mode so I can interrogate it from the host.

May 072017
 

So, I’ve done some tweaks to the prototype… namely fixing some wire assignments. I also had to drop my 1kΩ resistor on the input to a 100Ω as the voltage drop of the 1k was too high.

At the moment, I am seeing ~3V at the MCU, which is good enough.

Beneath the afro of wires, is the prototype.

… and this is the PWM LED control in action (animated GIF). So PWMing the output enable of a 74LS374 works, and doing the same on a 74HC574 should too.