# ADC ## Overview An analog-to-digital converter (ADC) is a device that converts analog signals into digital signals. The ADC APIs provide a set of common functions for ADC data transfer, including: - Opening or closing an ADC device - Obtaining the analog-to-digital (AD) conversion result **Figure 1** ADC physical connection
![](figures/ADC_physical_connection.png "ADC_physical_connection") ## Available APIs **Table 1** APIs of the ADC driver

Category	API	Description
Managing ADC devices	AdcOpen	Opens an ADC device.
Managing ADC devices	AdcClose	Closes an ADC device.
Obtaining the conversion result	AdcRead	Reads the AD conversion result.

## Usage Guidelines ### How to Use The figure below illustrates how to use the APIs. **Figure 2** Using ADC driver APIs
![](figures/using-ADC-process.png "using-ADC-process.png") ### Opening an ADC Device Call **AdcOpen** to open an ADC device. ```c DevHandle AdcOpen(int16_t number); ``` **Table 2** Description of AdcOpen

Parameter	Description
number	ADC device number.
Return Value	Description
NULL	Failed to open the ADC device.
Device handle	Handle of the ADC device opened.

For example, open device 1 of the two ADCs (numbered 0 and 1) in the system. ```c DevHandle adcHandle = NULL; /* ADC device handle / /* Open the ADC device. */ adcHandle = AdcOpen(1); if (adcHandle == NULL) { HDF_LOGE("AdcOpen: failed\n"); return; } ``` ### Obtaining the AD Conversion Result ```c int32_t AdcRead(DevHandle handle, uint32_t channel, uint32_t *val); ``` **Table 3** Description of AdcRead

Parameter	Description
handle	ADC device handle.
channel	ADC device channel number.
val	AD conversion result.
Return Value	Description
0	The operation is successful.
Negative number	Failed to obtain the AC conversion result.

### Closing an ADC Device Call **AdcClose** to close the ADC device after the ADC communication is complete. ```c void AdcClose(DevHandle handle); ``` **Table 4** Description of AdcClose

Parameter	Description
handle	ADC device handle.
Return Value	Description
None	No value is returned if the ADC device is closed.

Example: ```c AdcClose(adcHandle); /* Close the ADC device. */ ``` ## Example This following example shows how to use ADC APIs to manage an ADC device on a Hi3516D V300 development board. The basic hardware information is as follows: - SoC: hi3516dv300 - The potentiometer is connected to channel 1 of ADC device 0. Perform continuous read operations on the ADC device to check whether the ADC is functioning. Example: ```c #include "adc_if.h" /* Header file for ADC APIs */ #include "hdf_log.h" /* Header file for log APIs */ /* Define device 0, channel 1. */ #define ADC_DEVICE_NUM 0 #define ADC_CHANNEL_NUM 1 /* Main entry of ADC routines. */ static int32_t TestCaseAdc(void) { int32_t i; int32_t ret; DevHandle adcHandle; uint32_t Readbuf[30] = {0}; /* Open the ADC device. */ adcHandle = AdcOpen(ADC_DEVICE_NUM); if (adcHandle == NULL) { HDF_LOGE("%s: Open ADC%u fail!", __func__, ADC_DEVICE_NUM); return -1; } /* Perform 30 times of AD conversions continuously and read the conversion results. */ for (i = 0; i < 30; i++) { ret = AdcRead(adcHandle, ADC_CHANNEL_NUM, &Readbuf[i]); if (ret != HDF_SUCCESS) { HDF_LOGE("%s: tp ADC write reg fail!:%d", __func__, ret); AdcClose(adcHandle); return -1; } } HDF_LOGI("%s: ADC read successful!", __func__); /* Close the ADC device. */ AdcClose(adcHandle); return 0; } ```