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Circuit didn't work

This week's circuit did not end up working even after 3-4 iterations. Basically there is no response from the chip..

Based on Neil's design

  • I wired the chip's VCC to the IC2 to power it with 3.3V but this does not seem to work in my own circuit. The way I had it configured, the chip's VCC was being fed 3.3V which in theory should work (the operating voltage of the attiny44 is 1.8v to 3.3V. Using a multimeter, I measure the voltage coming out of the voltage regulator to be 1.8V. Ali the TA thinks this might be because too much is being powered by the voltage regulator and causing the chip not to function at the 1.8V (too close to operating limits). Not sure why?
  • Also the IC2 requires a capacitor on in and out but there does not seem to be one on in in Neil's design?

Too many things wired to 3.3V

The MEMS analogue microphone requires a 3.3V regulated voltage to work which is fed to it by using a SOT23 LM3480IM3-3.3/NOPBCT-ND regulator (referred to as IC2). I unfortunately wired the 3.3V power to VCC at several positions (including the VCC of the programming header). This caused many issues.

Rewired VCC

I rewired the whole circuit so that only the MEMS VDD input is wired to a 3.3V input. I hope this is correct?

Not enough PWM ports

There are only 4 hardware PWM ports on the attiny44 and two of them are MOSI/MISO so I used the MOSI port for LED PWM. Brian said that should be fine for an LED. Not sure what to do for more intensive loads?


I use the MOSI pin for PWM

Milling too deep!!

I have never had this problem but as you can see, the toolpaths are way too deep! I didn't change anything from the defaults and so I don't know what is wrong.

Default milling settings screenshot

I tried reducing the cut depth to 0.002in but this did not help

Final result

Other than the paths being too deep and it not working (lol), I think my boards finally look a bit more pro! :)

Routing is hell so I used a ground backplate

I used the copper vinyl sticker to make the backplate and used wires through holes I drilled to connect the grounds to the backplate


I was not able to simply export the vias to PNG to drill on the mill. I had to export the vias as position, open them as gimp, reduce each via to a point, lie about the diameter of the outline mill to make it a hole. Otherwise it makes a circle-shape trace instead of a punch hole. Surely there is a better way to do this?

Eagle FAB RGB placement wrong

The RGBA on the eagle library and the datasheet are off