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   Foone🏳️‍⚧️ (foone@digipres.club)'s status on Tuesday, 04-Nov-2025 11:21:38 JST Foone🏳️‍⚧️

   California uses a radio-tag system called FasTrak for vehicles, and recently they sent me a new tag.

   So naturally I had to open up the old tag, right?

   • Embed this notice
     Foone🏳️‍⚧️ (foone@digipres.club)'s status on Tuesday, 04-Nov-2025 11:21:34 JST Foone🏳️‍⚧️

     in reply to

     It's a 16-bit RISC architecture, 256 bytes of RAM, 4K +256B of flash memory

   • Embed this notice
     ✧✦Catherine✦✧ (whitequark@mastodon.social)'s status on Tuesday, 04-Nov-2025 11:21:34 JST ✧✦Catherine✦✧

     in reply to

     @foone oh hey, an MSP430

   • Embed this notice
     Foone🏳️‍⚧️ (foone@digipres.club)'s status on Tuesday, 04-Nov-2025 11:21:35 JST Foone🏳️‍⚧️

     in reply to

     Datasheet says this runs at 1.8v to 3.6v, and ultra-low power consumption: 250 µA at 1mhz, 2.2v, 0.7 µA on standby, and 0.1µA when off (with RAM retention)

   • Embed this notice
     Foone🏳️‍⚧️ (foone@digipres.club)'s status on Tuesday, 04-Nov-2025 11:21:36 JST Foone🏳️‍⚧️

     in reply to

     This thing in the corner under the designation BP1 is an SFM-1640A by East Electronics, an SMD External-driveen Piezo Transducer.

     This thing beeps when you change the number of occupants or (sometimes) when it gets scanned.

   • Embed this notice
     Foone🏳️‍⚧️ (foone@digipres.club)'s status on Tuesday, 04-Nov-2025 11:21:36 JST Foone🏳️‍⚧️

     in reply to

     And the microcontroller is a TI MSP430F2121 Mixed Signal Microcontroller.

   • Embed this notice
     Foone🏳️‍⚧️ (foone@digipres.club)'s status on Tuesday, 04-Nov-2025 11:21:37 JST Foone🏳️‍⚧️

     in reply to

     It's officially called a T21 Internal Tag Fixed Battery Switchable

     (some models don't have the switch)

     part number R2916-219

   • Embed this notice
     Foone🏳️‍⚧️ (foone@digipres.club)'s status on Tuesday, 04-Nov-2025 11:21:38 JST Foone🏳️‍⚧️

     in reply to

     This is the closest I was able to get to a non-blurry picture.
     It's not super complicated inside: Two main big components, a battery (non-rechargable lithium!) and a switch. The antenna is built into the PCB itself.

   • Embed this notice
     ✧✦Catherine✦✧ (whitequark@mastodon.social)'s status on Tuesday, 04-Nov-2025 11:52:20 JST ✧✦Catherine✦✧

     in reply to

     @foone it doesn't support a 32 MHz crystal

   • Embed this notice
     Foone🏳️‍⚧️ (foone@digipres.club)'s status on Tuesday, 04-Nov-2025 11:52:21 JST Foone🏳️‍⚧️

     in reply to

     I can't be sure what mode it's in without examining the registers, but it looks like they gave it a 7.2mhz crystal instead of the expected 32mhz. So the CPU might be running at 3.6mhz instead of the nominal 16mhz

   • Embed this notice
     Foone🏳️‍⚧️ (foone@digipres.club)'s status on Tuesday, 04-Nov-2025 11:52:22 JST Foone🏳️‍⚧️

     in reply to

     that's all I can tell without being able to photograph it better (I'm doing this while laying down) or do some continuity testing

   • Embed this notice
     Foone🏳️‍⚧️ (foone@digipres.club)'s status on Tuesday, 04-Nov-2025 11:52:23 JST Foone🏳️‍⚧️

     in reply to

     That battery is the Tadiran TL-4934 Lithium Thionyl Chloride.
     Nominal capacity of 1 amp-hour.

     if they're running this thing at 10µA on average this battery will last about 11 years