update 3: framebuffer is getting real, loooong battery life

A project log for Pix-Watch - stm32l4 based smartwatch

A smartwatch with an cortex m4f at heart. using awesome components and imagination to bring it to life.

8bit-bunny8bit-bunny 01/19/2016 at 06:006 Comments

Ramon here,

i have been working again on the watch a few days ago till now, with 2 main things in mind: framebuffer and extending the battery life

i succeeded in both, mainly in battery life: 370 hour standby (17 hour runtime @ 24mhz) time (no accelerometer yet) (total powerdraw: 1.35mA)

which is like 15 days of standby on a 500mAh lipo!

right now i am working on porting all graphic commands to use the framebuffer.

only downside of the framebuffer is: it consumes half of the teensy 3.2's RAM.

but thanks to rossum's microtouch framework we can still have 9kilobytes of RAM for apps, which is 1/8th more than an Arduino mega!

also, cool thing of the framebuffer is: alpha blending is possible, and some people might have seen a video of me demonstrating it. but for those who didn't, here's the video:


Montassar wrote 01/23/2016 at 19:16 point

Nice update, I thought you gave up this one :) The "GFX_test_Dots" is captivating, is it custom code or using a library ? 

You mentioned you already optimized battery life, but in case you want, you can check Kenvin's new series about Low Power "tricks"

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8bit-bunny wrote 01/24/2016 at 12:13 point

i simply ported the ili9163c library from sumotoy to work with a framebuffer :)
and i was using deepsleep mode already, which disables almost everything, right now i'm expirimenting with the hibernate function, it now consumes 0.31mA when in hibernation (teensy 3 snooze library)

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Montassar wrote 01/25/2016 at 15:49 point

Cool, I'm looking forward to the future updates.

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8bit-bunny wrote 01/24/2016 at 12:14 point

also, i ditched the azerowatch ecause it just doesn't do it regarding power consumption, or someone else is willing to create a similar low power library for the atsamd21

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8bit-bunny wrote 01/25/2016 at 16:03 point

thanks, i'm currently also discussing with the same guy who designed the zerowatch for this pcb, he's willing to do this, though it will be 4 layers for the pcb (same as zerowatch) and can be ordered at oshpark in the future i hope (also asked if he would opensource the cad files) :)

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Montassar wrote 01/25/2016 at 16:26 point

You mean designing it ? Do you plan to use the teensy directly onto the pcb or customly solder the chips ? The same TFT LCD is available on aliexpress with the flex to solder directly onto the board. 

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