// Test Arduino (328p) clock pre-scaling for power consumption

// mode 0 - Do nothing - normal 16Mhz clock
// mode 1 - Clock divide by 2 - 8Mhz
// Mode 2 - Clock divide by 4 - 4Mhz
// Mode 3 - Clock divide by 8 - 2Mhz
// Mode 4 - Clock divide by 16 - 1Mhz

// Results:
// 0 = 39.6 40.1
// 1 = 27.2 27.7
// 2 = 22.0 22.1
// 3 = 17.4 17.3
// 4 = 15.3 15.3

int test_mode = 4;

// I found this at ftp://82.140.81.3/pub/atmel/_AVR_MCUs_8bit/_WITH_USB/AT90USBKEY_CD/starterkits/STK525-USBKEY/firmware/at90usb128-usbkey-demo-3enum-host-mouse-1_0_4/Atmel/at90usb128-usbkey-demo-3enum-host-mouse/at90usb128/demo/ms_mouse_host_mouse/doc/html/a00101.html
#define 	Set_prescaler(x)   (CLKPR = (1<<CLKPCE),CLKPR = x)

// Using this variable works around a bug in some systems
// See: http://arduino.cc/forum/index.php/topic,59965.msg432768.html
int delay_time = 10000;

void setup() {
  Set_prescaler(test_mode);
}

// This is supposed to be a constant 'load'. Looping continuously may
// cause variable current consumption, so I'm hoping a long delay will
// mean the chip is in a 'constant' state.
void loop() {
  delay(delay_time);
}