update 8: performance boosts

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.

mon ramon ra 02/27/2017 at 18:100 Comments

ramon here with a small update again

just wanting to state the performance increase per watt in floating point math (for alpha blending/antialias) between the original design (teensy 3.2) and the new design (stm32l4)

first i'd like to point that the stm32l4 is at least 3x as power efficient as the teensy 3.2 spec wise

in reality more like 4x as the teensy 3.2 requires a seperate bootloader ic which used power too.

then the floating point math.... the teensy 3.2 doesn't have a fpu at all, so calculations are slow for sure, on the stm32l4 however, the speed is over 7x compared to the teensy, as the stm has a fpu.

compared to power effifiency, this is about a factor 28 or so (fpu math / watt)

also, might change from the stm32l476 to the stm32l496 with 320k of sram in the future, for bigger apps, and it's more power efficient too. (91micro amps / mhz versus 100 micro amps / mhz)