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Events/2020/AVR: Difference between revisions
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/* | |||
This code takes ADC readings at a constant rate and prints them to the serial | |||
port. Output is formatted to be CSV-compatible - simply copy the contents of | |||
the serial monitor to a text file. The channels to be digitized are specified | |||
by the array 'channelSequence' - use the channel names defined directly above | |||
it in the code. Sample rate is controlled by setting 'freq' - this expects an | |||
integer value in Hz. The ADC voltage reference is controlled by 'ADCref'. Use | |||
one of the three values defined immediately above it. | |||
Written exclusively for the Arduino Uno - makes direct use of the ATMEGA328's | |||
low-level registers, so not guaranteed to work on other microcontrollers. | |||
-nj 2020-10-12 | |||
*/ | |||
// --- User-set variables for sample rate, ADC range and channels sampled | |||
// Redefine this to change the frequency of ADC readings. | |||
// One channel is stable at up to ~833.33 Hz | |||
const uint16_t freq = 150; // Hz | |||
// ADMUX values to select ADC voltage reference. Table 23-3. | |||
#define EXT 0b00000000 // External voltage reference | |||
#define VCC 0b01000000 // 5 V | |||
#define I11 0b11000000 // 1.1 V | |||
// Redefine this to change what voltage the ADC uses as Vmax. | |||
const uint8_t ADCref = I11; | |||
// ADMUX values to select different channels. Table 23-4. | |||
#define A_0 0b00000000 | |||
#define A_1 0b00000001 | |||
#define A_2 0b00000010 | |||
#define A_3 0b00000011 | |||
#define A_4 0b00000100 | |||
#define A_5 0b00000101 | |||
// Redefine this to change which channels get digitized and in what order. | |||
volatile uint8_t channelSequence[] = { A_0, A_1, A_2 }; | |||
// --- Variables used for sampling the ADC | |||
const volatile uint8_t maxIndex = sizeof(channelSequence) - 1; // sizeof(array) / sizeof(array[0]) for non-byte types | |||
volatile uint16_t rawADC[sizeof(channelSequence)]; | |||
volatile uint8_t index; | |||
volatile unsigned long sampleTime; | |||
volatile bool readComplete = false; | |||
String sample = ""; | |||
const uint16_t CTCmatch = 62500 / freq - 1; // Note deliberate use of integer division | |||
// --- Variables used to control recording | |||
volatile bool btnReleased = false; | |||
bool recording = false; | |||
// --- setup() and loop() | |||
</pre> | </pre> | ||