OpenWrt One - celebrating 20 years of OpenWrt

[Piotr Dymacz]

Hi Forest,

On 10.01.2024 15:18, Forest Crossman wrote:
> On Tue, Jan 9, 2024 at 4:52 AM John Crispin <john at phrozen.org> wrote:
>>
> ---SNIP---
>>
>> * Why is there no USB 3.x host port on the device?
>> - the USB 3.x and PCIe buses are shared in the selected SoC silicon,
>> hence only a single High-Speed USB port is available
> 
> Perhaps you've already considered this, but it may be possible to
> route the shared PCIe/USB 3 traces to both an M.2 slot and a USB 3
> host port using a high-speed dual-channel differential 1:2/2:1
> switch/mux. It wouldn't enable both interfaces to be used at the same
> time, but it would make it possible to select which interface is
> enabled using a GPIO pin. Then U-boot could either automatically
> enable one port or the other depending on what devices it detects
> (e.g., enable PCIe and disable USB 3 if a PCIe device is connected,
> otherwise enable USB 3 and disable PCIe), or it could be statically
> configurable via a U-boot environment variable.

I suppose this should work (I couldn't find anything which would prevent 
using pure h/w analog mux on the bus with a runtime configuration) but I 
don't think there is a way to actually test it without a custom hardware 
(usually anything which doesn't exist in reference design/s from the 
chipset vendor must be tested in target configuration). Assuming bus 
speeds we are talking here about, I'm not sure this can be tested with 
some home-based tinkering ;)

I'm afraid that might delay the project but I will ask around.

>  From some quick searching, the switches/muxes that would enable this
> cost less than $1 each in qty. 1000. For a <$100 product I understand that
> may be too much of an increase to the BoM cost and PCB complexity, but
> I think users would really appreciate being able to choose between
> being able to add an M.2 SSD, WiFi card, or SATA controller and being
> able to plug in a USB 3.x 2.5 GbE adapter, SSD/flash drive, WiFi
> dongle, or 5G modem.

This would also require a bit more current capacity in the USB Type-A 
connector if we decide to make it 3.x.

-- 
Cheers,
Piotr