Next hardware platform

[mungewell]

Just a day has passed since the release and I'm already thinking about next board(s)....

I think this is a real good candidate:
https://www.waveshare.com/wiki/RP2350-Touch-LCD-2

It has:

• lots of pins broken out.
• internal circuitry for charging Li-Ion cell
• mounting bosses, which would make a 3D printed enclosure relatively easy.

I wonder whether the existing PT-Thrifty board could be mounted sideways on the headers (for testing), we only need to connect the 'short side' and can then fly-wire power/ground/others.

• LTC/nLTC must be adjacent GPIO
• BLINK/QTRclock must be adjacent GPIO
• others can be reassigned at will.

We'd need to avoid any pins already in use for LCD/Touch...

[mungewell]

Waveshare headers:

Since we have 9 pins down the sides of Thrifty: 9 * 2.54 = 22.86, we'd fit between headers.

[mungewell]

I had a pretty successful effort at a prototype for testing the RP2350-Touch-LCD-2, obviously a special PCB would be better suited but this hack gets something workable to experiment with.

The PT_Thrifty board can sit on a single row header along the P1 header of the board. Mostly this header is has GPIOs which are used on the Camera connector, but we're not planning on using that. There are some GPIOs which are used by the LCD so those needed to be isolated... easiest way is to cut off the top of the socket (placed onto the P1 header).

This is the pinout which then works. I re-allocated the PIOs/GPIOs to match this, arrows show flywires and brackets are signals which exist - but only internally so don't need connections.

This doesn't look to bad in real life:

Note: the edge the PT_Thrifty board next to J1 can be trimmed a little for a better fit on the connector, but there is a track 'outside' of J2 - so don't trim that side!

[mungewell]

I then spent way too many hours with an issue that it wouldn't Jam'Sync... turns out there's something the LTC_RX signal needing a pull-up into the 'touch' board (GPIO setting fixed it).

I implemented the same UI as PT_Thrifty; one button and the LCD is flood-filled with colour (instead of the NeoPixel). There's a branch here, but likely not too much will be done here - just a playground.

https://github.com/mungewell/pico-timecode/tree/pt_thrifty_touch

Open to suggestions on how a simple interface could use the touchscreen, but don't want it to be too complicated. Yet to be seen whether the LCD is quick enough for displaying frame counter.

[mungewell]

Found out why PT-Thrifty wasn't working with my Android phone:
https://source.android.com/docs/core/interaction/accessories/headset/plug-headset-spec

As we're AC coupled (via the cap), we need to add a pull-down resistor (> 1K0) so it sees it as a mic, and not a collection of switches.