Introduction

This chapter describes the usage of the 12-bit analog-to-digital converter (ADC) of RTL8721Dx.

The ADC of the RTL8721Dx is a successive-approximation register (SAR) ADC, which includes up to 7 external channels, 1 battery measurement channel and 1 internal channel. The ADC supports continuous sampling, software triggered sampling and timer triggered sampling. The result of ADC conversion is stored in the result register and can be read on demand.

The following table shows the description of channels.

Description of channels

Channel	ADC channel ID	Pin name	Input voltage (V)
External normal channel	CH0~CH6	PB13~PB19	0~3.3
External BAT_MEAS	CH7	BAT_MEAS	0 ~ 5
Internal AVDD33	CH9	N/A	0~3.3

Usage

To use ADC auto mode, the following steps are mandatory.

1. Enable clock and function of ADC module.

   RCC_PeriphClockCmd(APBPeriph_ADC, APBPeriph_ADC_CLOCK, ENABLE);
   

2. Configure the ADC pinmux according to the pinmux specification.

   For example, call the following functions to use ADC0.

   Pinmux_Config(_PB_19, PINMUX_FUNCTION_ADC)
   PAD_InputCtrl(_PB_19, DISABLE);
   PAD_PullCtrl(_PB_19, GPIO_PuPd_NOPULL);
   PAD_SleepPullCtrl(_PB_19, GPIO_PuPd_NOPULL);
   

3. Set the default parameters, and modify ADC mode. After that, channel list and other parameters can be modified in ADC_InitStruct if needed.

   ADC_StructInit(ADC_InitTypeDef *ADC_InitStruct);
   ADC_InitStruct->ADC_OpMode = ADC_AUTO_MODE;
   

4. Initialize ADC and then enable ADC.

   ADC_Init(ADC_InitTypeDef *ADC_InitStruct);
   ADC_Cmd(ENABLE);
   

5. Read ADC sample data. You can use polling mode or interrupt mode to acquire ADC sample data.

   • Polling mode:

     ADC_ReceiveBuf(u16 *pBuf, u32 len);
     

   • Interrupt mode:

     ADC_INTConfig(ADC_BIT_IT_FIFO_OVER_EN | ADC_BIT_IT_FIFO_FULL_EN, ENABLE);
     InterruptRegister((IRQ_FUN)ADCIrqRxHandler, ADC_IRQ, NULL, INT_PRI_MIDDLE);
     InterruptEn(ADC_IRQ, INT_PRI_MIDDLE);
     ADC_AutoCSwCmd(ENABLE);