CH32V003 / CH32X035: How to configure the OPA

[boreack]

Hi,

While testing the chip, I found something a I don't understand (one more thing  ).
The example for the OPA (from the CH32X035 example zip, but must be similar) seems to configure the OPA in one pin, and the ADC in another pin.

As my understanding, que input signal must be in the OPA pin (PA7 in the example), and internally the OPA will send the signal amplified to the ADC pin (PA4)? So I only need to read the ADC_Channel configured for that pin.

This is the example code from WCH:

Code: [Select]

********************************** (C) COPYRIGHT *******************************
 * File Name          : main.c
 * Author             : WCH
 * Version            : V1.0.0
 * Date               : 2023/12/26
 * Description        : Main program body.
 *********************************************************************************
 * Copyright (c) 2021 Nanjing Qinheng Microelectronics Co., Ltd.
 * Attention: This software (modified or not) and binary are used for
 * microcontroller manufactured by Nanjing Qinheng Microelectronics.
 *******************************************************************************/

/*
 *@Note
 *OPA PGA routine:
 *OPA2_CHP0--PA7
 *OPA2_OUT--PA4
 *The negative input pin of OPA is an internal pin, and when the positive
 *input voltage is given, the output gain is 4 times.
 */

#include "debug.h"

/*********************************************************************
 * @fn      OPA2_Init
 *
 * @brief   Initializes OPA2.
 *
 * @return  none
 */
void OPA2_Init( void )
{
    GPIO_InitTypeDef GPIO_InitStructure = {0};
    OPA_InitTypeDef  OPA_InitStructure = {0};

    RCC_APB2PeriphClockCmd( RCC_APB2Periph_GPIOA, ENABLE );
    GPIO_InitStructure.GPIO_Pin = GPIO_Pin_7;
    GPIO_InitStructure.GPIO_Mode = GPIO_Mode_IN_FLOATING;
    GPIO_Init( GPIOA, &GPIO_InitStructure );

    OPA_InitStructure.OPA_NUM=OPA2;
    OPA_InitStructure.PSEL = CHP0;
    OPA_InitStructure.NSEL = CHN_PGA_4xIN;
    OPA_InitStructure.Mode=OUT_IO_OUT0;
    OPA_InitStructure.FB=FB_ON;
    OPA_Init( &OPA_InitStructure );
    OPA_Cmd(OPA2, ENABLE );
}

/*********************************************************************
 * @fn      ADC_Function_Init
 *
 * @brief   Initializes ADC collection.
 *
 * @return  none
 */
void ADC_Function_Init(void)
{
    ADC_InitTypeDef  ADC_InitStructure = {0};
    GPIO_InitTypeDef GPIO_InitStructure = {0};

    RCC_APB2PeriphClockCmd(RCC_APB2Periph_GPIOA, ENABLE);
    RCC_APB2PeriphClockCmd(RCC_APB2Periph_ADC1, ENABLE);

    GPIO_InitStructure.GPIO_Pin = GPIO_Pin_4;
    GPIO_InitStructure.GPIO_Mode = GPIO_Mode_AIN;
    GPIO_Init(GPIOA, &GPIO_InitStructure);

    ADC_DeInit(ADC1);

    ADC_CLKConfig(ADC1, ADC_CLK_Div6);

    ADC_InitStructure.ADC_Mode = ADC_Mode_Independent;
    ADC_InitStructure.ADC_ScanConvMode = DISABLE;
    ADC_InitStructure.ADC_ContinuousConvMode = DISABLE;
    ADC_InitStructure.ADC_ExternalTrigConv = ADC_ExternalTrigConv_None;
    ADC_InitStructure.ADC_DataAlign = ADC_DataAlign_Right;
    ADC_InitStructure.ADC_NbrOfChannel = 1;
    ADC_Init(ADC1, &ADC_InitStructure);

    ADC_Cmd(ADC1, ENABLE);
}

/*********************************************************************
 * @fn      Get_ADC_Val
 *
 * @brief   Returns ADCx conversion result data.
 *
 * @param   ch - ADC channel.
 *            ADC_Channel_0 - ADC Channel0 selected.
 *            ADC_Channel_1 - ADC Channel1 selected.
 *            ADC_Channel_2 - ADC Channel2 selected.
 *            ADC_Channel_3 - ADC Channel3 selected.
 *            ADC_Channel_4 - ADC Channel4 selected.
 *            ADC_Channel_5 - ADC Channel5 selected.
 *            ADC_Channel_6 - ADC Channel6 selected.
 *            ADC_Channel_7 - ADC Channel7 selected.
 *            ADC_Channel_8 - ADC Channel8 selected.
 *            ADC_Channel_9 - ADC Channel9 selected.
 *            ADC_Channel_10 - ADC Channel10 selected.
 *            ADC_Channel_11 - ADC Channel11 selected.
 *            ADC_Channel_12 - ADC Channel12 selected.
 *            ADC_Channel_13 - ADC Channel13 selected.
 *            ADC_Channel_14 - ADC Channel14 selected.
 *            ADC_Channel_15 - ADC Channel15 selected.
 *
 * @return  none
 */
u16 Get_ADC_Val(u8 ch)
{
    u16 val;

    ADC_RegularChannelConfig(ADC1, ch, 1, ADC_SampleTime_11Cycles);
    ADC_SoftwareStartConvCmd(ADC1, ENABLE);

    while(!ADC_GetFlagStatus(ADC1, ADC_FLAG_EOC));
    val = ADC_GetConversionValue(ADC1);

    return val;
}


/*********************************************************************
 * @fn      main
 *
 * @brief   Main program.
 *
 * @return  none
 */
int main(void)
{
    u16 ADC_val;

    NVIC_PriorityGroupConfig(NVIC_PriorityGroup_1);
    SystemCoreClockUpdate();
    Delay_Init();
    USART_Printf_Init(115200);
    printf("SystemClk:%d\r\n", SystemCoreClock);
    printf( "ChipID:%08x\r\n", DBGMCU_GetCHIPID() );
    OPA_Unlock();
    OPA2_Init();
    ADC_Function_Init();
    while(1)
    {
        ADC_val=Get_ADC_Val(ADC_Channel_4);
        printf("ADC_val  %04d\r\n",ADC_val);
        Delay_Ms(500);
    }

}
Greetings.