✧✦Catherine✦✧Jun 29
new cat toy!
Show thread✧✦Catherine✦✧Jun 29

it's alive and talking to me!

as usual, the SPI peripheral implementation in it is kinda finicky, and it actually doesn't work with the default #GlasgowInterfaceExplorer SPI controller (because it's not fully compliant with SPI, oops)

i'll fix the SPI controller in a bit

Show thread✧✦Catherine✦✧Jun 29
this is definitely not an ADIS16488 and if it's a clone of it, then they have taken some remarkable liberties with the idea of a "functionally identical" replacement
Show thread✧✦Catherine✦✧Jun 29
Show thread✧✦Catherine✦✧Jun 29
the delta-angle and delta-velocity functionality appears to simply not exist, which excludes this being a faithful clone of either adis16488 or adis16375
Show thread✧✦Catherine✦✧Jun 29
oh, i just realized that it has a "product ID" register that clearly says 0x4068 (16488). so it's supposed to be a clone of ADIS16488 then. it's just a very bad one
Show thread✧✦Catherine✦✧Jun 29

this thing doesn't seem to have a magnetometer or a barometer, it's just an accelerometer and a gyroscope. not even very good ones, they're probably on par with what your cellphone has, if not worse

i think some enterprising company (possibly Shenznen Firepower Control Co. Ltd. based on @poppyhaze's research) has realized they can make a lot of money selling ADIS16488-style devices that only barely work at a half of their sticker price from AD

Show thread✧✦Catherine✦✧Jun 29

oh... it has a GD32F103 inside. there are even, conveniently, pads with SWD routed to them

firmware dumping time? firmware dumping time.

Show thread✧✦Catherine✦✧Jun 29
we have SWD!
Show thread✧✦Catherine✦✧Jun 29
the source code is not protected (i am reading out valid values), but for some reason my dump memory command is encountering errors; most likely a misunderstanding of ADIv5.2
Show thread✧✦Catherine✦✧Jun 29

it looks like sometimes it works and sometimes it doesn't

very bold of a vendor to call it a "good device" when in fact it seems to be bad

Show thread✧✦Catherine✦✧Jun 29
nevermind, it works fully once i attach a logic analyzer. for one reason or the other, adding a few pF of capacitance to the pins is what it needed
Show thread✧✦Catherine✦✧Jun 29
here's a firmware name: WM_KT-EX9-10_2.12_GD103.bin
Show thread✧✦Catherine✦✧Jun 29

did someone build the firmware with -funroll-loops or what

this is a part the code that copies static mutable data into RAM from Flash. it goes on for kilobytes

Show thread✧✦Catherine✦✧Jun 29
there's actually a few loops in the middle doing the same memcopy operation. i think the compiler smokes crack
Show thread✧✦Catherine✦✧Jun 29
although, a horrifying thought is that this is just what the original code looked like
Show thread✧✦Catherine✦✧Jun 29

OH I GOT IT

i finally tracked down the source of this device, and also the gyroscope vendor

the WM_KT-EX9-10_2.12_GD103.bin in the firmware name most likely refers to the gyro:
https://en.ktjmyq.com/html/2024/MEMS_0526/141.html

KT-EX9-1 - MEMS GYROSCOPE - KaiTuo Precise Instrument Co., Ltd-accelerometer,Gyro,MEMS,MEMS Gyro,MEMS Accelerometer,KTJB1,KTFG,KTEX

FEATURESTriaxial, digital gyroscope, ±450° sec dynamic range ±0 05° orthogonal alignment error,0 3&

Show thread✧✦Catherine✦✧Jun 29

i'm wrong. the KT-EX9-1 device has a public datasheet and some key values don't match

this could be a custom one-off or something?

Show threadSDRHoernchen
@whitequark.. Or just a shady copy of a copy, due to usage? Returns probably happen rarely, and the buyer might be a bit desperate.
Jun 30 at 12:24amWeb
Show thread✧✦Catherine✦✧Jun 30
@SDRHoernchen it's possible, but I think it's somewhat unlikely