[Arm-netbook] EOMA-68 tablet/laptop/engineering-board PCB schematics design underway

[luke.leighton]

ok, right... we come full circle... :)

i looked at the GL860A, and went, "this is silly, it's an 8-bit
microprocessor", so i looked again online and found yaay!  sparkfun
have a 640x480 camera they're doing (TCM8230MC) and there's even
source code using libstm32.a (yaay!) and everything:
    https://github.com/adamgreig/followingrobot
    https://www.sparkfun.com/products/8667
    https://randomskk.net/projects/robot2/robot2_eagle.zip

so with a 6mhz PCM output onto the camera sensor's clock line, the
data can be read apparently with DMA, yaaay!  as there's no processing
required (like in the followingrobot project), i'm confident that a
72mhz STM32F would have enough cycles to do audio.

whiiich, again, thank you to adrian here, he helped me track down a
PCM (Class D) audio driver circuit, it's actually trivial and
something i've encountered before with motor controllers
(http://www.robotpower.com/osmc_info/) although using 10kW not 1 watt
:)  but... it's a MOSFET H-Bridge aaand a low-pass filter.  DUH.  if
you run PCM fast enough (1mhz), a simple filter does a decent job.

and for the microphone, a simple Op-Amp (LM396) takes care of
amplifying the microphone up to the point where the ADC of the STM32F
can read it without noise.

just one thing... does anyone know of a circuit using Op-Amps where i
could do a 2nd stage volume control that would increase the gain, even
if it was only 2 bits (one bit increasing the sensitivity by x5 and
another say increasing by x20 or something)?  or maybe a PCM output,
levelled out by a capacitor, then used as the volume control (i'm
concerned about running out of pins on the STM32F)

... or a good forum to ask these questions on? :)

it's all gooood.  almost there.
http://rhombus-tech.net/community_ideas/kde_tablet/

l.