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What are the digital input and output pins on AVR?
AVR® 8-bit microcontrollers control applications through their digital Input and Output (I/O) pins. These pins can monitor any voltage present as a high impedance input and supply or sink current as a high or low voltage digital output. These pins are usually organized in groups of eight and referred to as a port.
What happens when PORTx is disable on AVR?
When the PORTx register disables the pull-up resistor the input will be tri-stated, leaving the pin left floating. When left in this state, even a small static charge present on surrounding objects can change the logic state of the pin. If you try to read the corresponding bit in the pin register, its state cannot be predicted.
Can you turn off pull ups on AVR ports?
Normally, the pull-up enabled state is fully acceptable, as a high impedance environment will not notice the difference between a strong high driver and a pull-up. If this is not the case, the PUD bit in the MCUCR Register can be set to disable all pull-ups in all ports.
Why are floating inputs not allowed on AVR?
Floating inputs should be avoided to reduce current consumption in all other modes where the digital inputs are enabled (Reset, Active Mode and Idle Mode). The simplest method to ensure a defined level of an unused pin is to enable the internal pull-up.
How does an AVR take an analog reading?
The channel that the analog reading will be taken from is selected, then, to start a conversion, the ADSC bit (found in ADCSRA) is turned on. Once the conversion is complete, the ADC hardware automatically clears the ADSC bit.
How do you read the top 8 bits of an AVR?
To do this, we need to read the top 8-bits (bits 9–2), not the bottom 8 bits. This is easily achieved using the ADLAR bit, which, when set to 1, will make the ADC result left justified. This means that instead of needing to read both result registers (ADCH and ADCL) and doing some bit manipulation, we can directly read ADCH and forget about ADCL.