Fadecandy Test Jig

This is a simple one-off test fixture that's designed to facilitate in-circuit debugging of the Fadecandy firmware, and doing reliable low-volume production.

My prototype consists of:

• An ugly hand-wired perfboard
• 0.1"-spaced pogo pins which connect to the Fadecandy board's "hacker port" as well as its output header
• A standard ARM JTAG header for firmware development using an external JTAG adapter
• A 2-LED string of WS2811 LEDs, for verifying the timing of the Fadecandy outputs
• A Teensy 3.0 board which coordinates production and testing tasks

The board is intended for two separate use cases:

• During firmware development, it's a simple breakout board for the JTAG port
• During low-volume production, the Teensy installs firmware and performs electrical testing

This board is a work-in-progress. This directory contains Teensyduino sketches which run on the onboard Teensy. More information about the hardware will be included later.

Hardware tidbits

• JTAG port uses 10K pull-up resistors to Fadecandy's 3.3v rail on all signals.
• Pogo pins are 2x Digi-Key part ED8178-16-ND
• Big green button next to pogo-pins to initiate programming/test

Teensy 3.0 pin assignment

Pin	Description
Gnd	Shared ground
Vin	+5V power for testjig itself
0	Teensy RX, Fadecandy TX
1	Teensy TX, Fadecandy RX
2	To ground via green button
3	Fadecandy TCLK (SWCLK)
4	Fadecandy TMS (SWDIO)

Testjig Firmwares

• production
  • Programs bootloader and initial firmware image
  • Runs electrical tests
  • Communicates with the DUT processor using Serial Wire Debug
• serial_passthrough
  • Teensyduino sketch
  • Appears as a USB serial port device
  • Passes through access to the DUT serial port
  • When the green button is held, acts as a loopback for the DUT serial port, as one way to enter FC-Boot.

Contact

Micah Elizabeth Scott <micah@scanlime.org>