[Arm-netbook] IC for analog and digital buttons (EOMA-68)

Luke Kenneth Casson Leighton lkcl at lkcl.net
Thu Aug 7 09:13:21 BST 2014

On Thu, Aug 7, 2014 at 8:51 AM, Miguel Garcia <gacuest at gmail.com> wrote:
> 2014-08-07 8:57 GMT+02:00 Luke Kenneth Casson Leighton <lkcl at lkcl.net>:
>>  ...except do try to find one that's a bit less than $0.95 in volume!!
>> http://www.futureelectronics.com/en/technologies/semiconductors/comm-products/i2c/Pages/4007443-PCA9575PW2,118.aspx?IM=0
> If SPI is better, MCP23S17 is an interesting alternative.

 faster for sure.  I2C tops out safely at 4mhz.  SPI i believe can do 25mhz.

> $1.00 en volume:

 blegh - and you need 2 of them _and_ 2 analog ICs as well. that's
starting to make the STM32F103 (64-pin variant) look attractive.  and
i know you can get that at around the $2.50 mark in 10k volumes.

 *sigh* ok do you really need that USB Flash thing?  because of a) the
cost (at least $4.50) b) the number of ICs (4) it's starting to tip in
favour of the STM32F again, i get the feeling you'd be better off
wiring up the STM32F as a USB 1.1 device.  you'll also need to wire up
the UART to the EOMA68 interface and a couple of other pins to put it
into "firmware upload" mode, but that's ok.

 the advantage there is that i have some GPL'd KiCAD designs with
STM32F already in them (or have found some out there when i last


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