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• current state of TeV:

  Eris • 09/14/2022 at 20:52 • 0 comments

  The current prototype (v0.4) works but has the following issues:

  -there is a bug in the trackpoint circuit that currently requires annoying soldering hacks to bypass.

  -the zero of the trackpoint isn't exactly 3.3v/2 so i need digital potentiometers to set the zero for the opamps accordingly
  

  -i need to change the way the leds are driven, my current solution for getting a 5v logic level is stupid and i had to bypass it and drive the leds out of spec.

  The digital potis for the trackpoint need I2C because i only have 4 i/o pins on the mounting plate, but the ADC which i need because the rp2040's adc doesn't have enough resolution for my taste needs to be SPI because those are way cheaper and more available right now.

  so what i'm gonna do is use a buffer to only pass through data to the digital potentiometer when the chip select of the ADC isn't enabled.

  i'm also gonna use that same buffer to drive the leds by connecting it's Vcc to a diode connected to 5v so that for it 3.3v is a logic high and it's output is a logic high for the LEDs running at 5v.

  a significantly bigger problem is the case. i can't keep milling the cases, it's too much work for small badge production. i'm gonna try to remake the 3d model in freeCAD and try to get quotes for other people milling it as well as look into injection molding. if none of this works i'll get the case SLS printed in nylon.
  

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