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A project log for Tetent Timespy [gd0136]

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

kelvinAkelvinA 08/08/2022 at 16:234 Comments

The screen obtainable determines the dimensions of the watch. I want to have a screen larger than 2 inches, but it seems that any solution that exceeds 65mm in any axis would become bulky for my 50x42mm arm. The main requirement is low power consumption for an always-on-display and >=30Hz (ideally >= 60) refresh . 

I actually started thinking about this project again because I found this screen on AliExpress:

It's even 90Hz. Unfortunately, it's 78x67mm and there are no solutions to fit it on my wrist.

It's in the description that I found out about Memory LCD.

I looked into it and it seems like a nice e-paper display alternative. That 3.16 inch one caught my eye but I didn't look into it at the time because I had just found another OLED. It looks pretty nice, though I wonder how fast the refresh rate could be.
 I believe some wireframe UI version of #enSweepen [gd0096] could work on this, as well as easily suited for digital note taking (which is the reason why #Tetent Tiny [gd0040] was started) and #Interval Provisional [gd0097]. It doesn't really matter what OS the watch runs as long as it can run these apps, but it's more streamlined on the software side if the OS can use a unified codebase like MAUI.

Moving on, this is the OLED I eventually found:

Like the first OLED, it's a MIPI device. That makes it questionable if I can drive the display since it seems MIPI documentation is a guarded secret or something. The screen should be around 54.7x41mm, so it's still a tad on the small side.

Back to the reflective LCD, I found some more data on an Alibaba listing.

A 80mm long watch (76 + 2mm bezels) might be a bit of a stretch, but everything else sounds pretty good if I can actually buy it. It doesn't look like there's much availability on the internet.

It's like they're advertising straight at me. I have also been thinking of the possibility of using this screen on #SecSavr Suspense [gd0105] along with a 5 way button. From experience using the classic 12864 3D printer controller screens and the 3Devo, I'm not a fan of the rotary encoder push button.

Discussions

Daniel Grace wrote 08/08/2022 at 16:47 point

... I was just talking to someone on the adafruit discord about MIPI... that wasn't you was it? Just in case it's not, this is what I found for them:

https://focuslcds.com/mipi-display-serial-interface-dsi/

I assume you've already seen this, since I found it with like 10 seconds of searching for them.

  Are you sure? yes | no

kelvinA wrote 08/08/2022 at 16:56 point

No I'm not in the adafruit discord and no I haven't seen it. The last time I searched was probably a few years ago.

  Are you sure? yes | no

Daniel Grace wrote 08/08/2022 at 17:00 point

Since it wasn't my project, I didn't put much time into evaluating the site. My quick impression was that it probably had enough info to make something work, but it wasn't pretty dense and might not be the easiest to follow. Maybe it's enough for you though, I've been pretty impressed with your grasp of dense info in these logs.

  Are you sure? yes | no

kelvinA wrote 08/08/2022 at 18:04 point

Thanks for the compliment. While the info is sparse, it does look easier to follow than when I was researching MIPI CSI for trying to use an OV4689 directly. 

  Are you sure? yes | no