I'm looking for a way to build a USB key. I have a bit of experience with the Arduino, however for this project that seems to be a bit of overkill.
The key should contain a unique serial number (EEPROM?), either to be programmed or factory-set (whatever is easier). Besides the serial number, I need to control 3 LEDs. Each LED has 3 states (on, off & blinking).
I was think to start with a CP2102 based USB TTL UART.
The software (linux) should talk to the RS232 port and be able to retrieve the serial number, and set each LED to the 3 different states.
I read about I2C and SPI. I seems SPI is easier to control, but you need more pins to hook it up.
My questions are:
1) What would be the better protocol I2C or SPI (in terms of 'easy' implementation)?
2) Assuming you can't hookup the LED's and the EEPROM direct to the UART. I need some type PIC to facilitate the communication. What would be a could PIC for this?
Not sure if it matters but: once I have a working prototype, I need to be able to batch produce a few hundreds of these.