I've actually managed to sell a few kits, so that's exciting.

As I was getting them ready to sell, I wanted to make sure the little holtek chip on there was soldered on and working correctly. So I needed a some Quality Assurance to make sure I was sending out working stuff.

I came up with the following steps after I flash the holtek and power it up through the flashing tool to verify its operation:

1. Check that the pull up for the tilt switch is working. Get the multimeter and set it to voltage. Then press the black probe to the ground pin of SW1 and the red probe to the pull up side of SW1. It passes if it registers 3 volts.

2. Check that the enable pin for the Voltage regulator that feeds the nodemcu, U1, is off. The holtek chip should wait for the state of SW1 to change before it turns on the voltage regulator. Press the red probe to the enable pin of U1, the far left pad. This test passes if the multimeter reads 0 voltage or ground.

3. The next pin to check is the one the holtek uses to check if the nodemcu is done. Its labeled D3 on the nodemcu. That pin is set to input pullup on the holtek so it should read 3 volts. Take the red probe and place it on the D3 pin spot. Test passes if its 3 volts.

4. Now to check that a state change on SW1 will trigger the holtek to turn on the Nodemcu's voltage regulator, U1. Short the pads for SW1 with a jumper wire for several seconds and remove it. Now take the black probe and red probe and place them according to test 2. This time it should show 3 volts and that passes the test.

That gives me pretty good confidence that the holtek chip is soldered on correctly and programmed correctly.

The final test I could do, where pulling the D3 pin low will turn off the U1 voltage regulator, and I've done that on some of the boards. It doesn't seem to add much to the testing. It would find a software defect on the holtek but I've already proven that out, so it doesn't need to be done every board.