Can your system read less than 0.1 mA? If that's the limit of your detection, you can't say much about a number that is as close as 0.2 mA. Assuming ideal rounding error, it could be something like 1.499999999999 vs 1.500000000001 milliamp. Any digital measurement system will need more than one x the smallest possible reading to have a statistically supported result.
Sounds to me like he's talking about a 3.3v USB-Serial adapter - that seems to be the terminology used to refer to a 3.3v serial adapter, even if that use of "TTL" may not be strictly speaking correct.
All else being equal, when run at a higher voltage, hardware will consume more current, combined with the issue Chris pointed out above, this result doesn't seem surprising at all.
In general, did you remember to turn off the ADC before going to sleep? ADCSRA &=~(1<<ADEN) - turn back on after sleep with ADCSRA |= 1<<ADEN (I think you also have to throw away the first ADC reading after turning it back on, don't remember) - by default the chip leaves it on in sleep, which eats a couple hundred uA.
DrAzzy:
Sounds to me like he's talking about a 3.3v USB-Serial adapter - that seems to be the terminology used to refer to a 3.3v serial adapter, even if that use of "TTL" may not be strictly speaking correct.
All else being equal, when run at a higher voltage, hardware will consume more current, combined with the issue Chris pointed out above, this result doesn't seem surprising at all.
In general, did you remember to turn off the ADC before going to sleep? ADCSRA &=~(1<<ADEN) - turn back on after sleep with ADCSRA |= 1<<ADEN (I think you also have to throw away the first ADC reading after turning it back on, don't remember) - by default the chip leaves it on in sleep, which eats a couple hundred uA.
here is my code
void disableHardware() {
// radio.sleep(); // Set the radio transceiver in sleep mode
radio.powerDown(); // NOTE: The radio MUST be powered back up again manually
power_spi_disable(); // Disable the Serial Peripheral Interface module.
power_timer0_disable(); // Disable the Timer 0 module..
power_timer1_disable(); // Disable the Timer 1 module.
power_timer2_disable(); // Disable the Timer 2 module
power_twi_disable(); // Disable the Two Wire Interface module.
//power_usart0_disable(); // Disable the USART 0 module.
ADCSRA &= ~(1 << ADEN); // Ensure AD control register is disable before power disable
power_adc_disable(); // Disable the Analog to Digital Converter module