Driver for basic ADC functionality.
v0.0.0.1 Initial Commit
The driver provides only single shot, non-windowed operation of the ADC.
If the ADC hardware supports using multiple resolutions, the conversion is done using the resolution specified by the user in START.
Polled mode
Interrupt mode
In the Polled Mode, the application code explicitly starts a conversion on a specified channel, waits for the conversion to complete, and reads back the result.
In the Interrupt Mode, the application code explicitly starts a conversion on a specified channel. When the conversion is done, the ADC ISR is executed. The user can hookup a callback to this ISR, specifying any actions to be performed by the ISR, such as reading the result, performing arithmetic on it, and storing it to a buffer. To generate code for including a callback handler, tick the "Include harness for IRQ on conversion complete"- box in START.
An ADC conversion is started by calling <component_name>_start_conversion(adc_channel_t channel). A conversion will then be started in the ADC, and the result will be ready after a number of clock cycles. The function <component_name>_is_conversion_done() is used to poll if the result is ready. When the result is ready, it can be read using <component_name>_get_conversion_result(). The function <component_name>_get_conversion(adc_channel_t channel) combines all these operations into a single function: Start conversion, wait, and read result.
ADC conversion results are returned as datatype adc_result_t, which has 16 bits. The data is right-adjusted, and the number of bits used is dependent on the resolution of the ADC, or the chosen resolution if the ADC supports multiple resolutions. The function <component_name>_get_resolution() returns the number of bits in the result, and can be used to adjust or scale the result if needed.
The ADC Basic driver needs ADC hardware to perform conversions. When the user has selected a device and added an ADC component, the Driver field in the Component Settings pane in START will let the user select which timer driver to use, select Drivers:ADC:Basic to use the ADC Basic driver.
The Configuration Pane in START will display options that are dependent on the hardware used to implement the ADC driver. For example, an option may allow changing the number of result bits or clock prescaling used to drive the underlying ADC hardware.
The ADC Basic may be configured to use use the interrupt functionality of the underlying ADC. Make sure that global interrupts are enabled (using sei()) and that the Interrupt Controller, if present, is configured so that the ADC interrupt is serviced correctly.
#include <atmel_start.h>
volatile bool isr_executed = false;
volatile adc_result_t measurement;
volatile uint8_t measurement_normalized;
void adc_handler_cb(void){
measurement = ADC_0_get_conversion_result();
measurement_normalized = measurement>>(ADC_0_get_resolution()-8);
isr_executed = true;
}
int main(void)
{
/* Initializes MCU, drivers and middleware */
atmel_start_init();
// Test polled mode
// Get conversion from ADC CH0
measurement = ADC_0_get_conversion(0);
// Get 8 MSB of conversion result
measurement_normalized = measurement>>(ADC_0_get_resolution()-8);
// Test IRQ mode
sei();
ADC_0_register_callback(adc_handler_cb);
// Start conversion from ADC CH0
ADC_0_start_conversion(0);
// Wait for ISR to be execued
while (!isr_executed);
while (1);
}