maybe adding 12 groups of vias, even though there are 11 charlieplexed groups will make it easier to route around the hour LEDs? this PCB is starting to look like a @welshpixie mandala
oh no the coin cell ground pad and tabs interfere with the beautiful 11-sided spiral. maybe there's a small LiPo that would fit instead?
DRC says only 110 warnings! But 1273 errors, so maybe this clever design isn't quite ready.
#Kicad friends: is there a way to request tented vias on only one side? I'd like the spiral to be shiny on the top and covered on the bottom
thanks to a suggestion from @marble and the power of python, there are now a gross number of small circles in the F.Mask layer to un-tent the vias on only one side of the board.
Something is wrong: only three or four io lines seem to be functional, although they all pass the multimeter beep test
Seems that the cpu browns out when some of the charlieplexed pins are driven, which makes me suspect there might be solder bridges under the QFN package.
Turns out the secret is that the gpio config on the msp430fr2433 is unchangeable except for port1 pins 4-7 until you set the magic LOCKLPM5 bit in the PM5CTL0 register. Now all the LEDs work!
Somehow I had overlooked this totally unobvious disclaimer buried on page 316 of TI's 676 page data sheet for this chip.
Now with a 3D printed case and 22mm nato watch strap. Need to get a 35mm sapphire and maybe a wider band.
I've started porting the older Charliewatch animations to the bi-color version. I should rethink some of them now that we can distinguish the different hands.
The original Charliewatch boards, also with 0603 LEDs, fit entire inside the circle of the new layout. Despite increasing to 132 LEDs, it should still be routable on the two layers, assuming the fab will put them that close together.
@th this is so cool, and now I'm imagining it with white LEDs and a tinted acrylic cover 🤔
@pixls I made a white version of the single-color design, but the problem is that the forward voltage on the LEDs is too high, so once the battery drops below 3V it stops working. This means a few weeks instead of a several months of runtime with the red/yellow LEDs that can go down to 1.9V.
@th oh wow, wild. that does look great tho
@federico3 @pixls many of my watches are 24-hour, although the observation was that nine charlieplexed IO lines could drive 9*(9-2) = 72 = 60 + 12 LEDs. For the bicolor ones 12 IO lines can drive 12*(12-1) = 132 = 60 + 60 + 12 LEDs. There weren't any values that provided nice 24-hour dial combinations.
@th Very neat :)
For everyday use I would prefer it to make special moves only on special occasions (like end of the workday), but I assume thats presentation mode :)
@th omfg this is gorgeous! 🤩✨
All of the test Charliewatch boards fab'ed and assembled by Aisler work perfectly (other than things that I broke, like not noticing that this MSP430 requires load caps for the crystal). For the next rev I want to squeeze the LEDs closer together to shrink the watch face a bit, which might require violating the ERC.