Mystery GPS Tracker on a Supporter’s Car

Re:Mystery GPS Tracker on a Supporter’s Car by rurban on Tuesday March 29, 2022 @01:21AM (#30839038)

you configure modems still the same way. you still have modems in IoT devices. what changed are the capabilities, esp. the power states. these trackers can sleep most of the time, only wake up periodically, so they can survive on battery for several years.

most sensors are connected via I2C to the CPU. some weird ones via SPI. most GPS sensors are different, they connect mostly via UART. so you can connect to them directly, bypassing the CPU.

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Re:Mystery GPS Tracker on a Supporter’s Car by pantalaimon on Tuesday March 29, 2022 @01:58AM (#30839287)

> some weird^W fast ones via SPI

ftfy

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Re:Mystery GPS Tracker on a Supporter’s Car by rurban on Tuesday March 29, 2022 @11:20AM (#30843757)

block devices, yes. my GNSS sensor needs SPI btw.

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Re:Mystery GPS Tracker on a Supporter’s Car by pantalaimon on Thursday March 31, 2022 @12:29PM (#30869112)

MT3333? Yea that's an improvement over the UART interface where it just sends out the data no matter if the other side is listening or sleeping. With the SPI interface you get an interrupt and can read the data at your own pace.

But I2C would do too if they would offer a proper register interface as opposed to always expecting you to parse those verbose NMEA messages.

Oh and only generating an interrupt if the fix is valid would be nice! But they just shoehorned the SPI interface onto it, exposing exactly the same data as they would over UART. So if you have to wake up, parse the message and only then will you find out if you have a valid fix or can go back to sleep and try again.

Afaik they dropped the SPI mode in the newer chips though.

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