I've been working with the ATMEGA324P-20AU to read some data over SPI from five ADCs that are triggered (all at the same time) by a conversion pin. The conversion pin of each ADC is wired to one pin of the ATMEGA.
I would like to have the ATMEGA trigger each conversion at an adjustable rate between 1 Hz and 1 kHz. The conversion rate is adjustable in software. I would like to achieve at least 0.1 Hz resolution.
I've noticed that the ATMEGA324P-20AU has an external pin (TOSC1) that can accept an input from an external oscillator.
If I am to use the 16-bit timer of the AVR, and the main processor clock is 18.432 MHz, could someone suggest:
(1) The clock frequency that I should input to the TOSC1 pin using an external oscillator.
(2) Which pin should I use as the conversion pin for the ADCs? One of the OCnA or OCnB pins?