Well, after trying this and that, I'm starting to get desperated.

I do have a setup in which a µC is connected to the dev board using uart, it is expected to send some data to the cara.
TX of the µC is connected to RXD (pin 2 on dev board, pin 32 on module) of carambola.

I already tried a lot, using mmio to set registers (mmio 0x10000060 0x17, also tried mmio 0x10000060 0x1F but then thought that's wrong because it sets uart to gpio), checking wires and connections (even on the dev board & module) over and over again, but I don't seem to get any data out of carambola's ttyS0 ...

The µC is continously sending data (even checked it using a usb adapter, it works), but the carambola doesn't seem to listen (no output in the program, nothing from tail, cat or whatsoever).

Even installed a voltage divider to scale down the input signal (µC is driven by 5V), after figured out that cara's inputs are *not* 5V tolerant (in contrast to that other post gedass made ...) double checked that as well (puts out solid 3.35V from 5V source).

Still - not even noise on /dev/ttyS0


Can anyone provide some help ?

If you have not killed your Carambola, try using picocom picocom -b 9600 /dev/ttyUSB0. Short Carambola's TX & RX, and check if you see your characters echoing back. Sure, you have to install picocom first (opkg update; opkg install picocom).

@Saulius: it's about ttyS0 - that's the one not working.
Cara is fine, but I didn't manage to get ttyS0 working.

@tty: already did that. No change at all.
Also rebooted a couple of times.

[edit]
Well, blame me: Tried a lot, ended up using ssh to log onto cara board, used picocom to monitor tty activity and eventually found that I seem to have confused rx and tx on µC side ...

Thanks for the support !

Still, there is one question to be answered:
Are the GPIO's [esp. those used for uart] 5V tolerant ?

There wasn't a clear statement made yet.

dasMopo, read here: http://www.8devices.com/wiki_carambola/ ... xing_ttys0

Saulius, thank you for the info.

But that doesn't answer my question:
Are those inputs 5V tolerant or not ?

[Wasn't able to get that V2.2 datasheet referenced in another topic.]

I plan to have a custom board for the cara, but right now I only have some MAX232N lying around - those expect / produce 5V TTL signal levels.

That's why I'm asking.

It is covered in another forum thread. Read here: viewtopic.php?f=5&t=8