pYro_65:
Hi all,I'm writing a new TFT driver and I want to test it out by drawing an oscilloscope style wave form to get a benchmark on line drawing; I'm just struggling with the ADC functionality. I found many good articles for setting it up on a smaller mcu ( 168/328 ) however the 2560 data sheet is quite involved.
What I'm after is a ADC set to free running mode using an ISR to capture the readings. I have only a need for 8-bit resolution at a pre-scale value of 32 for 500khz sampling.
I used the example code below in an attempt to get something running, however an error reports ADFR as not being declared.ADCSRA |= ( 1 << ADPS2 ) | ( 1 << ADPS1 ) | ( 1 << ADPS0 ); // Set ADC prescaler to 128 - 125KHz sample rate @ 16MHz
ADMUX |= ( 1 << REFS0 ); // Set ADC reference to AVCC
ADMUX |= ( 1 << ADLAR ); // Left adjust ADC result to allow easy 8 bit reading
ADCSRA |= ( 1 << ADFR ); // Set ADC to Free-Running Mode
ADCSRA |= ( 1 << ADEN ); // Enable ADC
ADCSRA |= ( 1 << ADIE );
ADCSRA |= ( 1 << ADSC );
I also haven't seen much use of the DIDR register(s) is this important/beneficial? I'll keep searching, however any ideas/useful links would be great. 8)
According to the databook, to setup free running mode, you set bits 0, 1 and 2 of the ADCSRB register to 0. You also need to set bit 6 (ACME) to a 1 to enable single ended mode.
Also, strangely, the ADMUX bits 0 through 4 are in the ADMUX register, but ADMUX bit 5 is bit 3 of ADCSRB.
A classic example of "Plan Ahea
d"
There is no ADFR register. ADFR is in internal processor signal.