USB serial built-in into next SBCs

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mad_ady
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USB serial built-in into next SBCs

Post by mad_ady »

Here's a wild idea that might be worth considering - how about adding the usb-uart logic into the next SBC directly?

There are still people struggling to getting their boards to boot which don't have a uart for basic troubleshooting.

How hard/costly would it be to have a dual-purpose usb-otg port on a sbc that can have a jumper to change role? By default the jumper disables the usb-serial circuitry so the port behaves like a regular otg port, but when enabled, the port becomes usb client and exposes the uart port.

Since the usb bus is there, presumably you wouldn't need to add $10 worth of ICs and would just need to add the usb-uart interface and some multiplexer for the data lines.

Any ideas if this would be a feasible design? So that you would only plug in an ubiqutous usb cable and have access to the console?

Granted, you wouldn't have both uart and usb-otg at the same time, but maybe that is an acceptable compromise (that could be routed to other uart pins though)
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L67GS (Fri Jul 09, 2021 6:27 am)

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Re: USB serial built-in into next SBCs

Post by rooted »

I like it, although I have a couple of their UART devices most people likely don't and it could be of benefit.

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Re: USB serial built-in into next SBCs

Post by L67GS »

Great idea! From a tinkerer's point of view for certain. Plugging, unplugging, and having the interface hang from the UART plug leads to broken wires at the plug, I've replaced my plug about 3 times in the last year. I'd love to replace that thing with a sturdy male USB to male USB cable.

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Re: USB serial built-in into next SBCs

Post by odroid »

CP2102N and header/jumpers might take $3~4 if we consider manufacturing & test cost together.
But, most of B2B customers do not want to accept that price increasing. I think our B2B customers cover near 80% of our total sales volume.

Another concern is that USB 2.0 high-speed (480Mbps) signal quality should be affected by slow USB 1.1 (12Mbps) USB-UART bridge controller by path selecting of the header pins with poor jumper qualities.
The last concern is that the OTG dual-role feature must make the circuit more complicated and increases cost more due to the VBUS power input and output mode switching.

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Re: USB serial built-in into next SBCs

Post by mad_ady »

Ok, fair enough. Thanks for analyzing it!
I take it the B2B customers aren't complaining about boot problems and have uarts while troubleshooting...
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