As detailed in another thread, I’m doing serial I/O over the TX/RX pins on the 40-pin header on the back of the Terminal, using the pinouts as labeled here.
To get any data at all, I had to swap the wires to the TX and RX pins, i.e. I’ve connected the MIDI-in pin on the board (i.e. the one incoming data comes from) to the Terminal’s TX pin. That seemed wrong … until I remembered that the connector on the back of the Terminal is meant to plug into a Raspberry Pi. Does that mean the pinouts given are from the Pi perspective? In that case the pin labeled “TX” is the one the Pi would transmit on, making it the receive pin on the Terminal.
Is that what’s going on? (In which case the diagram should be fixed to describe the pins from the Terminal’s perspective…) Because if that’s not the issue, I have no other sane explanation for why the UART only works with the pins connected backwards!
I hadn’t even gotten as far as figuring-out what all of the labels in this diagram are actually referencing, but it does appear that the second row of pin labels (going from inside -> out) are those from the RasPi. I’m not much of a RasPi user, but all of the other signal names on graphics on the web generally match those in these two columns of the Seeed graphic.
It seems very safe to assume that they’re using the RasPi signal names/labels in this image, which is definitely counter-intuitive. And since there’s no key as to what any of the colors or columns mean, one can only guess or try to figure it out yourself – which isn’t the point of good reference documentation.
Your experimental evidence and a review of the RasPi pinout concurs with your conclusion – that the labels are wrong based on most users’ expectation, without some other explanatory text in the image.
That confirms my understanding of the pin ordering. But the issue remains that the naming of the pins is wrong, because the names seem to be copied from the RPi docs, so inputs are mislabeled as outputs and vice versa.
Also (as I noted on another thread, but I’m putting it here for completeness) there are more problems with the pin naming. The “5v” and “3v” pins, for example, describe power that would be provided by a Raspberry Pi — there’s not actually voltage available on those pins on the Terminal!
And that’s the main reason my MIDI efforts were failing. I wasn’t even powering the MIDI board.
