jerome arul

makes (almost) anything

output week

redesign phototransistor circuit

breakout these phototransistors onto their own boards
• more flexibility with board
• more pin outs
• can place sensors anywhere with jumpers


how to hook up phototransistor source

V2 motor driver board

v2 motor driver board with pinouts

redesign driver board
• see A4950 driver chip
• refer to neil's A4953
• installed schottky diode on 5v line, so that it doesn't reverse into my computer
• forward voltage / side for diode (pointy direction of triangle) is the cathode, has a line on the component.

i didn't look at the pinout diagram when i designed the board. whoops.
i designed them around "convenience" and "location".


motor driver traces png

pin-out southside:
pin 22 > PA23
pin 20 > PA19

pin-out northside:
pin 1 > PA00
pin 3 > PA02 - ANALOG
pin 5 > PA04 - ANALOG
pin 7 > PA06 - ANALOG

motor driver pins:
pin 12 > PA09 - ANALOG
pin 14 > PA11 - ANALOG


motor driver outline png

SAMD21 datasheet 33.8.8 (pg 804) lists Analog pins (0-19 ?)
quentin's SAMD21 pinout
mtm SAMD21 pinout


v1, v1.1, v2


phototransistor breakouts


reflowed only mcu and swd, used heat gun


v2 motor driver


edbg on linux

openocd didn't work again (same error)
doing it wrong (trying to boot thru usb)

edbg worked on linux over ATMEL ICE

debugging phototransistors

since i can't bootload both v1 and v2
debug with leonardo
aren't burnt out

Leonardo: I can read voltage on the phototransistor breakout board,
but not through phototransistor
only use ANalog pins


phototransistor doesn't work, only resistor values


phototransistor breakouts


debugging with a Leonardo

no serial print

able to upload on IDE


compiler settings - are fine

Arduino IDE (v18) able to load sketches
but weird that the board doesn't run the sketch.

serial print doesn't work. (nothing shows up)
board probably doesn't save sketch
serial print works on the Leonardo.


Get Board Info
doesn't see sketch, or serial number

• not plugged in: Multimeter shows no shorts.
• plugged in: Multimeter shows ~5V from 5v to GND, and ~3.2V from 3.3V to GND.
• plugged in: voltage across vddcore capacitor reads ~1.2V
• baud rates are the same on sketch and serial monitor
• tried different baudrates
• changed 'Serial' to 'SerialUSB' in sketch. nothing

probably a board issue:
(Not a Mac M1 issue. Tried it on another Macbook with Intel core.)
quentin suggests booting again.

burn bootloader
• need 2 usb ports !
• 2x5 JTAG SWD cable (thnks anthony)
• arduino 1.8

quentin and the ebdg guy fixed the edbg issues with Mac M1 this week!
"Removed MacOS dependency on hidapi library, native APIs are used"
• update "fab sam" library to v1.11 on arduino board manager

"burn bootloader" - success!

D11C bootloader via SWD to D21

serial test

number count - serial test sketch

keep counting!

simple h-bridge
one pin HIGH
one pin LOW

h-bridge sketch

motor runs!