ADC
Introduction
An ADC (Analog-to-Digital Converter) is a hardware module that converts analog signals into digital signals. In embedded systems and microcontrollers, ADCs are used to convert sensor or other analog input signals into digital data for further processing and analysis.It should be noted that in the W80x series chips, the analog conversion circuit of the ADC requires approximately 2MS to generate one data.
Function List
Initialization —— Initialize the ADC driver.
Configuration of ADC —— Configure ADC channels and parameters.
Register Interrupt Callback —— Registers a callback function for timer interrupts.
Get Single ADC Result —— Obtains the result of a single ADC conversion.
Get Polling ADC Result —— Obtains the result of an ADC conversion in polling mode.
Start ADC Interrupt —— Start ADC interrupt mode.
Stop ADC Interrupt —— Stop ADC interrupt mode.
Read Internal Chip Temperature —— Read the internal temperature of the chip.
Read Chip Voltage —— Read the supply voltage of the chip.
Calculate Voltage Value —— Calculate the actual voltage value based on the ADC result.
Function Overview
Resource Management: The W800 has 4 independent ADC input channels and 2 differential channels. Users can manage different channels according to specific needs.
Flexible Parameter Configuration: The ADC supports configuring the number of channels such as the number of channels and sampling gain to suit various application needs.
High Precision: The ADC has high-precision signal conversion capabilities, suitable for various precise measurement applications.
Interrupts and Callbacks: The ADC supports interrupts and callback functions, which can trigger callback functions upon completion of conversions, facilitating real-time data processing.
Temperature Sensing: Built-in temperature sensors allow for reading the internal temperature of the chip via the ADC.
Voltage Detection: The ADC can detect the chip’s supply voltage, facilitating power management.
Main Features
Initialize ADC
Before using the ADC, you need to call the wm_drv_adc_init() function to allocate resources for the ADC, using the wm_device_t structure to receive the ADC device identifier. Example:
wm_device_t *adc_dev;
adc_dev = wm_drv_adc_init("adc");
The first parameter specifies the device name, which is defined in the device table.
Warning
After initializing the ADC, if wm_drv_adc_deinit is not called, calling wm_drv_adc_init again will return NULL.
Configuring the ADC
To configure the parameters of the ADC device, call the``wm_drv_adc_cfg()`` function. Example:
wm_device_t *adc_dev;
adc_dev = wm_drv_adc_init("adc");
wm_drv_adc_cfg_t adc_cfg;
adc_cfg.adc_channel_count = 1;
/* set cfg */
...
wm_drv_adc_cfg(adc_dev, &adc_cfg);
The first parameter is a pointer to the ADC device, of type wm_device_t*.
The second parameter is a pointer to a structure containing the ADC configuration parameters, of type wm_drv_adc_cfg_t.
Registering a Callback
Call the function wm_drv_adc_register_callback() to register an ADC interrupt callback function. The adc_callback is a callback function that will be invoked when an ADC interrupt is triggered. The arg is a parameter passed to the callback function, which is not used in this example. Here is an example:
wm_device_t *adc_dev;
adc_dev = wm_drv_adc_init("adc");
void adc_callback(void *arg) {
printf("ADC interrupt triggered!\n");
}
wm_drv_adc_register_callback(adc_dev, WM_ADC_INTR_TYPE_ADC, adc_callback, NULL);
The first parameter is a pointer to the ADC device, of type wm_device_t*.
The second parameter is the interrupt type, which indicates different types of ADC interrupts. In the example, WM_ADC_INTR_TYPE_ADC triggers an interrupt triggered when ADC conversion ends. It can also be set to WM_ADC_INTR_TYPE_DMA for DMA (Direct Memory Access) interrupts.
Note that the w800 does not currently support ADC DMA transfers. WM_ADC_INTR_TYPE_COMP represents a comparator interrupt. WM_ADC_INTR_TYPE_MAX is the maximum value of the enumeration type, used for boundary checking. The type is wm_adc_intr_type_t.
The third parameter is the callback function, of type wm_drv_adc_callback_t.
The fourth parameter is private data passed to the callback function, of type void *.
Generating a Single Conversion Result
Call the function wm_drv_adc_oneshot() to perform a single ADC conversion and return the result. Here is an example:
wm_device_t *adc_dev;
adc_dev = wm_drv_adc_init("adc");
int32_t result;
wm_drv_adc_oneshot(adc_dev, 0, &result);
The first parameter is a pointer to the ADC device, of type wm_device_t*.
The second parameter is the ADC channel number, of type wm_adc_channel_t.
The third parameter is a pointer to an int32_t variable result, used to store the result of the ADC conversion.
Generating Continuous Conversion Results
Call the function wm_drv_adc_polling() to perform continuous ADC conversions and store the results in a buffer. Here is an example:
wm_device_t *adc_dev;
adc_dev = wm_drv_adc_init("adc");
int buf[10];
wm_drv_adc_polling(adc_dev, 0, buf, 10, 1000);
The first parameter is a pointer to the ADC device, of type wm_device_t*.
The second parameter is the ADC channel number, of type wm_adc_channel_t.
The third parameter is a pointer to a buffer that stores the conversion results, of type int*, used to store the polled ADC data.
The fourth parameter is the size of the buffer, of type uint16_t.
The fifth parameter is the timeout value in milliseconds, specifying when to stop polling after exceeding this time , of type uint32_t.
Starting ADC Interrupt
Call the function wm_drv_adc_start_it() to start the ADC interrupt, initiating conversions in interrupt mode. Here is an example:
wm_device_t *adc_dev;
adc_dev = wm_drv_adc_init("adc");
wm_drv_adc_start_it(adc_dev, 0);
The first parameter is a pointer to the ADC device, of type wm_device_t*.
The second parameter is the ADC channel number, of type wm_adc_channel_t.
Warning
Interrupt mode will output ADC collected data rapidly. Avoid time-consuming operations in the corresponding interrupt callback, and use wm_drv_adc_cal_voltage() to calculate the collected voltage.
Stopping ADC Interrupt
Call the function wm_drv_adc_stop_it() to stop the ADC interrupt, ending conversions in interrupt mode. Here is an example:
wm_device_t *adc_dev;
adc_dev = wm_drv_adc_init("adc");
wm_drv_adc_stop_it(adc_dev, 0);
The first parameter is a pointer to the ADC device, of type wm_device_t*.
The second parameter is the ADC channel number, of type wm_adc_channel_t.
Reading Temperature
Call the function wm_drv_thermal_sensor_read_temperature() to read the temperature value within the chip. Here is an example:
wm_device_t *adc_dev;
adc_dev = wm_drv_adc_init("adc");
int temperature_val;
wm_drv_thermal_sensor_read_temperature(adc_dev, &temperature_val);
The first parameter is a pointer to the ADC device, of type wm_device_t*.
The second parameter is a pointer to an integer that will store the read temperature value, of type int*.
Reading Voltage
Call the function wm_drv_adc_chip_voltage_read_vdd() to read the supply voltage of the chip. Here is an example:
wm_device_t *adc_dev;
adc_dev = wm_drv_adc_init("adc");
uint32_t voltage;
wm_drv_adc_chip_voltage_read_vdd(adc_dev, &voltage);
The first parameter is a pointer to the ADC device, of type wm_device_t*.
The second parameter is a pointer to a variable that will store the read voltage value, of type uint32_t*.
Calibrating Voltage
Call the function wm_drv_adc_cal_voltage() to calibrate the chip voltage. Here is an example:
wm_device_t *adc_dev;
adc_dev = wm_drv_adc_init("adc");
wm_drv_adc_cal_voltage(adc_dev, 3300);
The first parameter is a pointer to the ADC device, of type wm_device_t*.
The second parameter is an integer representing the raw value obtained from the ADC interrupt, with 3300 set as the raw value in this example.
Application Example
For a basic example of using the ADC, refer to: examples/peripheral/adc
API Reference
For more information on ADC-related APIs, refer to: