[coreboot] $7 cheap FT232H board as EHCI debug dongle for coreboot - would it work?

[Mike Banon]

Hi Kyosti, Thank you very much for your reply!

I will try to get a couple of these FT232H boards: perhaps just 1 is
required for the successful setup, but these boards are not common
(just 15 or 20 search results) so maybe its' a good idea to take 2 ;)

If this FT232H board works, it would be an ideal replacement both for
commercial AMIDebug Rx / Ajays NET20DC (because much cheaper) and
FX2LP (because no DIY will be required). Maybe this info could even be
added to the official coreboot wiki, but I don't have an account there
and it seems hard to get, so I'm using the DangerousPrototypes wiki

Will write an update when I'd get the boards and test them with AMD
G505S laptop. I'm curious what Lenovo G505S is writing to the coreboot
log while it boots

Best regards,
Mike Banon

On Sat, Mar 3, 2018 at 4:57 PM, Kyösti Mälkki <kyosti.malkki at gmail.com> wrote:
> Hi Mike
>
> On Sat, Mar 3, 2018 at 3:27 PM, Mike Banon <mikebdp2 at gmail.com> wrote:
>> Good day! I am looking for the dirt cheap EHCI debug dongle. Initially
>> I found these instructions for FX2LP -
>> https://www.coreboot.org/DIY_EHCI_debug_dongle - but they require a
>> lot of manual soldering/mods which depend on your boards revision and
>> I am not sure if the currently produced boards are 100% compatible
>> with the wiki instructions
>
> PCBs indeed have some variations. I pretty much abandoned all efforts
> with FX2LP. However, some people were able to emulate the discontinued
> net20dc dongle product with the FX2LP approach, to the level it was
> operational with proprietary windows kernel debugger.
>
>>
>> But then I noticed a coreboot has USBDEBUG_DONGLE_FTDI_FT232H option:
>> " Use this with FT232H usb-to-uart. Configuration is hard-coded to use
>> 8n1, no flow control "
>>
>> Kyösti Mälkki tested it " with gizmosphere/gizmo1 Explorer add-on
>> board, which exposes the following device:
>>    0x0403 Future Technology Devices International, Ltd
>>    0x6014 FT232H Single HS USB-UART/FIFO IC "
>> but gizmo1 is expensive and I am not a fan of the single board
>> computers (SBCs) : they all require the binary blobs which could
>> contain the scary backdoors
>>
>
> Just forget all the talk about gizmo1, it was just the way I was able
> to test it i.e. I had the hardware at hand.
>
>> However, there are $7 cheap FT232H boards with USB available at AliExpress:
>>
>> https://www.aliexpress.com/item/NEW-CJMCU-FT232H-Multifunction-High-Speed-USB-to-JTAG-UART-FIFO-SPI-I2C-Module/32818305310.html
>>
>> I plan to get a couple of these boards, connect them to each other
>> with 1P 2.54mm wires, plug the 1st board into master PC
>> (coreboot-PC-under-debug) USB 2.0 port and the 2nd board into slave PC
>> (another coreboot PC which will be logging the debug info)
>>
>> Please tell me: could this setup work in theory, or there are obvious
>> shortcomings that could prevent it from working?
>>
>
> Sounds good with three wires, cross RX&TX, add GND. Only the 1st board
> (DUT) has to be FT232H, 2nd can be regular uart-to-usb like FT232R or
> PL2103(?), This FT232H board also does the job of external SPI flash
> recovery with flashrom.
>
> And.. kudos for Nico H for the initial FT232H init sequence code.
>
> Kyösti