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[T] Use CM4 for its MIPI DSI feature?

A project log for Tetent TimerSpy [gd0136]

A wearable PDA / smartwatch with a Tetent [gd0090] input method.

kelvinakelvinA 10/27/2022 at 23:431 Comment

[00:45]

While I've spent most of today computing my options for the #T^2 TyMist [gd0138], I started to have concern for the methods of controlling the OLED for this project too. I found these relevant projects:

I also don't think I'm going to be able to squeeze and fold over the ready-to-go driver.

I think that the blue board is wider than the screen! For years I've wished that board got a minimisation makeover because it's not easy thinking of ways to fit it into an enclosure.

The board uses the TC358870XBG Toshiba chip, but it's a dense BGA so manufacture could get a bit difficult.

Remembering that the CM4 supports DSI where the CB1 doesn't, I went to investigate futher:

Using this calculator, the bandwidth needed for 90Hz is between 2.8 and 3Gbps, so it should be a case of wiring things up and writing some drivers... not like I've ever written drivers (and in Linux no less) before. Speaking of Linux, I have been looking around to see how involved it could be to spin up -- but more importantly, maintain -- a custom distro, but this distro's changelog seems managable and this distro was apparently made as a side project, so maybe I'll manage. I've been interested in Powerpoint OSes since about 10 years ago, so I've had a feeling that there would be one reason or another that Future Me would make an actual OS [skin / distro] one day. Anyway, I might want to read up on content like this log to see what goes into driver dev.

I'd have to start looking into alternatives to the CM4 if I don't want to pay inflated prices for one. Last time I checked, I heard that the backlog for stock was going to be sometime mid 2023 soooo not sure about that one. Considering that I'm likely going to have the Timespy as unofficial #Teti [gd0022] and #T^2 TyMist [gd0138] controllers, it might make sense to have a basic edition that uses an SPI/I2C display (and perhaps runs off #Tetrinsic [gd0041] / the M032 series microcontroller). I'm still eyeing that 2.7" Sharp display, even if it's more expensive than I'd like:

Discussions

kelvinA wrote 10/30/2022 at 22:30 point

CM4 and alternatives that support MIPI: >£50 or out of stock

Toshiba's TC358870XBG: £8 on Aliexpress

The choice is relatively straightforward.

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