I have an Atmega328 chip I am trying to debug. I have a sketch that blinks an LED and echoes back things received over the RX/TX pins. I am using the "Import Arduino Sketch" feature in Atmel Studio 7. I want to use the internal 8 MHz clock.
The timer seems to be too slow by a factor of 2. I tell the LED to blink every second, but it takes two seconds. When I send text over the serial port I receive back gibberish, which is probably due to the baud rate not being the 9600 I want it to be.
I looked at the memory fuse to verify that I am using the internal clock. I also tried setting the clock prescaler to 1 in the sketch code.
Here is the section of the data sheet related to the clock frequency: http://ww1.microchip.com/downloads/en/DeviceDoc/ATmega48A-PA-88A-PA-168A-PA-328-P-DS-DS40002061A.pdf
My fuse settings seem to be OK, I disabled the 8x divisor and specified to use the 8MHz internal clock:
The clock prescaler information is on page 47, essentially it says I need to make the most significant bit a 1 to allow changes to the rest of the bits, then I change the other bits to 0 to set a prescale factor of 1. If I try setting it to a factor of 2 the time delay is made worse by a factor of 2 and has a total of 4 seconds delay when the code wants 1 second.
void setup() {
CLKPR = (1 << CLKPCE); // enable a change to CLKPR
CLKPR = 0; // set the prescale factor to 1
pinMode(greenLED, OUTPUT);
Serial.begin(9600);
analogWrite(greenLED, 15);
delay(1000);
analogWrite(greenLED, 0);
}
void loop() {
analogWrite(blueLED, 15);
delay(1000);
analogWrite(blueLED, 0);
delay(1000);
String text;
if (Serial.available()) {
text = Serial.readString();
Serial.println("Echo: " + text);
}
delay(30);
}
What other settings could be affecting the internal clock?
