[v0.1] Simplify bootloader entry

[whitequark]

The ID pin based bootloader entry scheme is highly inconvenient and requires using an illegal USB cable. Most end users will probably only need to enter the ROM bootloader once, so a test point is fine. I can see developers entering the ROM bootloader more often, so a button in parallel with a test point (which could be DNP) would be quite nice, especially on a high density board like this.

[vpalatin]

I find the trick highly convenient, but whatever ;-)
if you are planning to re-use part of the original firmware, it does include a 'dfu' command over the USB-serial console to switch it back to bootloader mode, you don't need special hardware most of the time:
https://chromium.googlesource.com/chromiumos/platform/ec/+/7a16e40adb108eaedb3a46619fcdf99cdd9a1b9d

[whitequark]

if you are planning to re-use part of the original firmware, it does include a 'dfu' command over the USB-serial console to switch it back to bootloader mode

Yeah and the command is broken... Instead of all this error-prone complex stuff just use a button.

[whitequark]

I think the command might actually be broken because of #1? I don't know how exactly it works, but the symptoms are that I can enter DFU mode but trying to flash anything instantly resets the device. I haven't tried it with the workaround for #1 yet.

[whitequark]

Sorry, I understand I probably sound quite hostile, that's not my intention. I've just had a lot of trouble with both USB PD and USB PD debuggers and after a few months of it that gets frustrating.

[dnschneid]

Buttons are nice as long as you can access them when the unit is enclosed in its enclosure and including it doesn't cause the enclosure to be larger than absolutely necessary (since any increase in case size results in more torque on the Type-C plug).

I think the USB-ID trick is especially convenient for us since we've been using the trick across multiple internal boards for years, so our devs tend to have them on-hand. Never had an issue with it (although it's best to plug in the micro-B side before the usb-A side).