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This repository has been archived by the owner on Sep 15, 2024. It is now read-only.
Start conversion and end of conversion (EOC) signals
Successive approximation ADC
2) Operating ADC in atmega328p using C avr lib:
To operate the ADC in the atmega32, you will need to study the ADMUX of the multiplexer which encodes the ADC pins and the status and control
register ADCSRA of the avr:
ADMUX: ADC multiplexer selection register:
ADMUX Register Bits
AREF Truth table
The ADLAR Bit
MUX Bits
ADSCRA: ADC Control and Status Register:
ADCSRA Register Bits
ADC Start Conversion bit
To start the ADC Conversion, setting the bit ADSC of the ADCSRA register to true is an essential step, furhter more the ADIE enables the interrupt service routine for the ADC conversion onComplete and the ADIF is set to true when the conversion is completed
A/D Conversion time
ADCL: ADC Low Byte Register
ADCH: ADC High Byte Register
For more about the internals of the ADC, here is a good article showing the operation of an ADC (MCP3008) with the raspberry pi in depth
Steps of implementing the ADC protocol using AVR lib c:
Adjusting the ADMUX register: to enable the ADC protocol, the interrupt service handler and the clock pre-scaler to valid clock greater than 200k HZ from the Fosc value (frequency of the crystal oscillator): --Jump to ADMUX Docs--
Start the conversion on an ADC_MUX code which encodes for ADC0...ADC7 according to a truth table: --Jump to A/D Conversion Docs--
/* define analog ADC pins based on the multiplexers codes */#defineADC_MUX0 ((const uint8_t) 0x00)
#defineADC_MUX1 (ADC_MUX0 + 0x01)
#defineADC_MUX2 (ADC_MUX1 + 0x01)
#defineADC_MUX3 (ADC_MUX2 + 0x01)
#defineADC_MUX4 (ADC_MUX3 + 0x01)
#defineADC_MUX5 (ADC_MUX4 + 0x01)
#defineADC_MUX6 (ADC_MUX5 + 0x01)
#defineADC_MUX7 (ADC_MUX6 + 0x01)
...
voidAnalog::Adc::startConversion(constuint8_t&PIN) {
/* setup ADMUX */ADMUX=0b01000000 | PIN; /* 1 for REFS0 for (VREF = VCC) */ADCSRA |= (1 << ADSC); /* the last step: start conversion */
}
Read the analog data using uint16_t Analog::Adc#analogRead() inside the interrupt service subroutine ISR(ADC_vect) {...} and then re-start conversion to trigger the interrupt service handler again for continous monitoring:
uint16_tAnalog::Adc::analogRead() {
volatileuint8_tadcl=ADCL; /* ADCL must be read before ADCH */volatileuint8_tadch=ADCH;
return ((0x00 | adch) << 8) | adcl; /* concatenate the 2 (8-bit registers) in a 16-bit software register */
}
#**#* Ccoffee Build tool, manual build, alpha-v1.#*#* @author pavl_g.#*## define work directory# 1) print the current working directory to a string value
pwd=`pwd`# cut the working directory from its end by a one '/' delimiter
project="${pwd%/*}"# cut the working directory from its end by a one '/' delimiter again
rootProject="${project%/*}"# pass the value of the dire
clibName=('libHelloAnalogRead')
# AVR-DUDE properties
BAUD_RATE='57600'
PORT='/dev/ttyUSB0'
CHIP='atmega328p'
CHIP_ALIAS='m328p'
PROGRAMMER='arduino'# Common Variables contain colorssource${rootProject}'/CommonVariables.sh'source${rootProject}'/AVR__HOME.sh'
output=${project}'/output/'${clibName}
Navigate to the AVR-Sandbox/HelloAnalogRead/build/ and run:
cd ../AVR-Sandbox/HelloAnalogRead/build/
./build
To compile only use ./compile.
To read from the serial port, run sudo ./readPort.