group assignment:

• use the test equipment in your lab to observe the operation of an embedded microcontroller

We first brainstormed different things that we could measure on the board. The easiest thing to do was verifying that each component worked and the connections worked as expected.

Multimeter

We started with the multimeter to probe various parts of a Xiao that was running a game.

• Resistance measurements
  • we recorded readings of about 9.8 kOhm and 6.6 kOhm on qpad
  • a bunch of stuff hooked up so resistance measurement is different
  • screen include their own pull up resistors to the SDA and SCL pins on the Xiao -> 2 built-in resistors are in parallel with the 2 that we added -> equivalent resistance is lower
  • usb cable -> sends voltage and corrupts reading
  • 9.99 when testing a detached resistor
  • if you take off soldering and measure it, it should say 10k

Modifying board

• use the solder as a wire LOL to pull out the pins that we wanted to measure
• apparently not a good idea in general because the wires act as an antenna and can measure random stuff in the “ether”/environment
• need to pull out pins to measure

Oscilloscope

• Touch pad pin
  • quentin touch test
  • probe pin (to pad) and gnd
  • clicked auto
• I2C signal clock line
  • probe clock line, can see clock rising and falling
  • can see repeating pattern
• I2C signal data line
  • better to use logic analyzer than oscilloscope
  • can see the signal is coming but need logic analyzer to decode
  • on one clock cycle can send a lot of data per cycle so it was v fast (40khz)
• Both lines at the same time
  • looks weird bc signal is too fast?
  • it looked kinda strange bc two signals were at diff scales
  • not a good idea to see digital protocol on oscilloscope

Power

• power w oscilloscope
• first hook up to multimeter to see that power output is correct
• multimeter wasn't measuring anything
• power xiao and measure voltage across it to check that reading is 3.3 V (using the multimeter to check that its working)
• changed wires on output supply
• it was a contact issue on the wires
• outputting 3.3 V and seeing 3.2 V
• now we can power with power supply
• power with 3.3 V
• draw is 0.042 A