On Wed, Aug 6, 2014 at 9:57 AM, krasi gichev krasimirr@gmail.com wrote:
I suspect that we are not looking at the complete picture here. Don't you have some more sensors to add on the I2C? Like accelerometer, magnetometer, maybe light sensor (for auto brigthness) and so on? Maybe battery monitoring? I see that you are discussing about using I/O expanders and ADC chips. Not to say that IN YOUR CASE you have to use microcontroller - just to show some points that could help you to take the right decision. . Using I/O expander means that you need several chips - at least two. This will take some board space and pin connections. Don't forget that beside I2C lines (SDA, SCL) you might need some (maybe one, maybe two) interrupt lines.
i've added 2 EINTs to the specification for exactly this purpose.
(ROM) bootloader with support for UART, SPI, I2C and so on. I would propose STM32 for example (it is quite well supported by open source tools and code base).
this is the original that i used in one of the early prototype tablet pcbs, it's very good, however the low-cost ones (STM32F103) don't do USB, you have to go to the $5 variants to get USB.
i think, manuel, if you draw out (even sketch) the full connectivity required then we can help evaluate.
l.