Trying to shift out from ATtiny85 to a shift register using the USI in SPI mode. I have Timer 0 running as slowly as possible (checked it was running by temporarily changing it to toggle a pin with an LED attached.) I have LEDs hooked up to USCK and DO so by rights I should be able to see them blinking as it sends.
What else do I need to do in order to get it shifting out in sync with Timer 0? All the examples I've looked at so far strobe the USI clock manually.
#include <avr/io.h>
int main(void){
DDRB = (1 << DDB2) | (1 << DDB1); // USCK & DO Output
DDRB &= ~(1 << DDB0); // DI Input
PORTB |= (1 << DDB0); // Pullup Resistor for DI
TCCR0A = (1 << WGM01); // Timer 0 in CTC Mode
OCR0A = 0xFF; // Timer 0 Compare A
TCCR0B = (1 << CS02) | (1 << CS00); // Prescaler / 1024
USICR = (1 << USIWM0); // USI 3 Wire Mode
USICR |= (1 << USICS0); // Timer 0 for USI 4-bit Clock Source
USIDR = 0x7F; // Why you no go? :c
USISR |= 0x08; // Set Counter to 8
USISR = (1 << USIOIF); // Clear Counter Overflow
while(1);
return 0;
}
