OpenStint

Appearance

Flashing the firmware ​

There is an automated job that compiles the firmware, check out releases. You'll need the .hex file. You can compile yourself, of course.

To flash the firmware, I use an ATMEL-ICE, sourceable from Mouser/DigiKey/etc. (~$100).

A much cheaper alternative is Adafruit High Voltage UPDI Friend - USB Serial UPDI Programmer (~$10).

Hardware ​

There are test points on the bottom of the transponder:

  • VDD powers the LDO, apply 4+ V here
  • VTG is a testpoint to check the LDO output voltage (should be 3.3V)
  • GND
  • UPDI is the programming pin

You can connect +3.3V directly to VTG, as the LDO has reverse current protection, and not use VDD (leave floating).

The v2 transponder's test point spacing is 2.54 mm / 0.1" away from each other. You need pogo pins to make proper contact. Adafruit, AliExpress.

Software ​

I use avrdude, the makescript use it as well.

Program both the fuses and the flash memory! The fuses are set to use the 20 MHz internal RC oscillator as a fallback if the crystal oscillator fails, as a fallback mechanism.

This does both:

make flash

OR:

avrdude -c serialupdi -p attiny816 -U "flash:w:main.hex" -U fuse1:w:0x02:m

Reading the transponder ID ​

The transponder ID is not stored anywhere: the firmware calculates it at boot from the chip's factory serial number (crc32(SIGROW.SERNUM0..9) % 10000000). The serial number is readable over UPDI, so tools/transponder_id.py can tell you the ID a board will transmit, over the same connection you flash with. No decoder or RF power-up needed. It is read-only and works on a blank chip too.

It needs Python 3 and avrdude 7.x or newer (for the sernum memory), with a serialupdi programmer:

$ python tools/transponder_id.py --port COM5
SERNUM : 2F510C111E4277A305BB
ID     : 4729780

When building a batch, add --csv and --label to collect a labelling list as you go. Each run appends a timestamp;label;sernum;transponder_id row:

python tools/transponder_id.py --port COM5 --csv transponders.csv --label 07

Run python tools/transponder_id.py --help for the rest of the options (--baud, --part, --avrdude).