feat(tools): add ESP32 ADC calibration and LUT linearization utility

[hippo5329]

Summary

Adds the adc_calibrate standalone diagnostic firmware utility:

• Sweeps the internal ESP32 DAC Channel 1 (GPIO 25) against BATTERY_PIN across 500 calibration iterations.
• Interpolates nonlinearities and outputs a formatted 4096-entry C Look-Up Table (ADC_LUT[4096]) over serial (115200 baud).
• Uses standard extra_configs = ../firmware/platformio.ini sourcing matching test_sensors, test_motors, and test_acc.

Verification

• 100% build pass across esp32, esp32s2, esp32s3, gendrv.

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[PaulBouchier]

Thanks for this.

I tested it on a Sparkfun Thing Plus with ESP32 WROOM. It seems to work as expected.

This is an "expert" tool - you need to have a good hardware understanding. You need to connect pin 25 to whatever your battery pin is, and either disconnect the battery sense electronics, or be confident that the DAC pin can overdrive the battery sense electronics, or else you may get erroneous results. In order to use the results, you need to insert the generated table into the LUT section of the config file. These are the sorts of in-depth documentation notes that really need to be in a documentation section that describes how to use the config file. I have in mind what that should look like, but at some point I want to organize the lower section of the config files a bit better by separating and commenting the sections like "syslog config" and I2C config and Lidar config. But I think that should be done in concert with documentation that tells how to customize the config file for your robot - which is something that doesn't really exist at the moment - what's in your wiki is the closest thing to that, but it doesn't go to this level of detail.