Teensy battery emulator with driver

[forderud]

Alternative to #33 for battery emulation.

Idea

• Teensy 4.x board that exposes a USB device with simulated battery pack status values that vary over time.
• Battery miniport driver to receive battery status events and forward them to Windows

USB protocol

1. Header: Send BATTERY\0 (8bytes), BATTERY_INFORMATION struct (36bytes) and a BATTERY_STATUS struct (16bytes) to host,
2. Afterwards, send BATTERY_STATUS structs (16bytes) on-demand to host when the status changes.

USB pipe: Use IN interrupt endpoint (max 64byte package size, max 255ms polling interval)

Teensy firmware

Teensy dev setup: https://www.pjrc.com/teensy/td_download.html

Implement the protocol above and transmit battery charge changes periodically.

Open questions:

• USB VID & PID: https://devicehunt.com/view/type/usb/vendor/16C0

Battery driver

Class=Battery - can most likely be combined with USB client driver

Notes:

• Overview of developing Windows client drivers for USB devices
• Might need to use continuous reader for polling the USB device.
• Sample: kmdf_fx2 - uses continuous reader to read from an interrupt endpoint.
• WdfUsbTargetPipeReadSynchronously for blocking read from interrupt endpoint during initialization

Implementation stages

1. Write Teensy firmware
2. Write a simple USB client driver that exposes IOCTL_BATTERY_QUERY_INFORMATION and IOCTL_BATTERY_QUERY_STATUS to user-space.
3. Merge USB driver with simbatt sample

Links

• https://learn.microsoft.com/en-us/windows-hardware/drivers/usbcon/usb-filter-driver-for-supporting-chargers
• https://www.usb.org/document-library/battery-charging-v12-spec-and-adopters-agreement

[forderud]

Closed in favor of #33