CH32V003 Programming: How to use GPIO as Output

In the Quick Start article we have learned how to setup development environment for CH32V003 MCU and how to compile and run an example code.

Now, we will see how we can set any GPIO Pin as output and set the Pin state as high or low.

We saw this in GPIO Toggle example code also but here in this article we will go in a little more deeper.

GPIO Ports

There are three port groups available in the MCU, Port A, C and D and in each group, number of pins are there.

Each Port pin can be configured as GPIO output and can be used in the application.

Uses of GPIO

GPIOs are mainly used for connecting LEDs, Relay control, providing status and control signals when connecting other devices or could be used for driving LCDs like OLED in SPI mode where SPI is emulated by GPIO bit banging, etc.

CH32V003 MCU Pinout

Read Datasheet

I would strongly recommend you to read the datasheet and go through the electrical characteristics section to know more about capability and limitation of GPIO port/pins. Like output current sourcing and sinking capability, etc.

Note about GPIO D7 / NRST

Please note PD7 is by default is configured as MCU reset pin, you need to configure it as GPIO by configuring it with WCH Link Programmer Utility or in the code.

Two options to change

1.

FLASH_Unlock();
FLASH_EraseOptionBytes();
FLASH_UserOptionByteConfig(OB_STOP_NoRST, OB_STDBY_NoRST, OB_RST_NoEN, OB_PowerON_Start_Mode_USER);
FLASH_Unlock();

2.

if your have WCH-Link Utility in your computer. You also can use it to change PD7 mode.

GPIO as Output Example Code for CH32V003

In order to configure any pin as GPIO output, you need to use the following code, let us call that in a function “GPIOConfig” as shown below, this will be the initialization code and need to be called before using the GPIO.

For any configuration, clock for that GPIO port needs to be enabled first.

Three Parameters are there for any GPIO when configuring as output

• GPIO_Pin: this is to define which Pin, for example for D0 it will be GPIO_Pin_0
• GPIO_Mode: to configure if the output will be an open drain (GPIO_Mode_Out_OD) or push-pull (GPIO_Mode_Out_PP)
• GPIO_Speed: to configure how fast you want control the GPIO. There are three options: GPIO_Speed_10MHz, GPIO_Speed_2MHz, GPIO_Speed_50MHz. This basically configures the drive strength of the GPIO internally.

void GPIO_Config(void)
{
GPIO_InitTypeDef GPIO_InitStructure = {0}; //structure variable used for the GPIO configuration

RCC_APB2PeriphClockCmd(RCC_APB2Periph_GPIOD, ENABLE); // to Enable the clock for Port D

GPIO_InitStructure.GPIO_Pin = GPIO_Pin_0; // Defines which Pin to configure
GPIO_InitStructure.GPIO_Mode = GPIO_Mode_Out_PP; // Defines Output Type
GPIO_InitStructure.GPIO_Speed = GPIO_Speed_50MHz; // Defines speed
GPIO_Init(GPIOD, &GPIO_InitStructure);

}

If multiple pins of same port needs to be configured with similar settings, you can write as shown below (GPIO D0 and D1):

void GPIO_Config(void)
{
GPIO_InitTypeDef GPIO_InitStructure = {0}; //structure variable used for the GPIO configuration

RCC_APB2PeriphClockCmd(RCC_APB2Periph_GPIOD, ENABLE); // to Enable the clock for Port D

GPIO_InitStructure.GPIO_Pin = GPIO_Pin_0 | GPIO_PIn_1; // Defines which Pin to configure
GPIO_InitStructure.GPIO_Mode = GPIO_Mode_Out_PP; // Defines Output Type
GPIO_InitStructure.GPIO_Speed = GPIO_Speed_50MHz; // Defines speed
GPIO_Init(GPIOD, &GPIO_InitStructure);

}

but, if you have different settings for different GPIO you can do like this (GPIO D0 and D1):

void GPIO_Config(void)
{
GPIO_InitTypeDef GPIO_InitStructure = {0}; //structure variable used for the GPIO configuration

RCC_APB2PeriphClockCmd(RCC_APB2Periph_GPIOD, ENABLE); // to Enable the clock for Port D

GPIO_InitStructure.GPIO_Pin = GPIO_Pin_0; // Defines which Pin to configure
GPIO_InitStructure.GPIO_Mode = GPIO_Mode_Out_PP; // Defines Output Type
GPIO_InitStructure.GPIO_Speed = GPIO_Speed_50MHz; // Defines speed
GPIO_Init(GPIOD, &GPIO_InitStructure);

GPIO_InitStructure.GPIO_Pin = GPIO_Pin_1; // Defines which Pin to configure
GPIO_InitStructure.GPIO_Mode = GPIO_Mode_Out_OD; // Defines Output Type
GPIO_InitStructure.GPIO_Speed = GPIO_Speed_2MHz; // Defines speed
GPIO_Init(GPIOD, &GPIO_InitStructure);

}

And, now suppose if you want to configure different pins of different ports, you can write code like this: (GPIO D0 and C1)

void GPIO_Config(void)
{
GPIO_InitTypeDef GPIO_InitStructure = {0}; //structure variable used for the GPIO configuration

RCC_APB2PeriphClockCmd(RCC_APB2Periph_GPIOC, ENABLE); // to Enable the clock for Port C
RCC_APB2PeriphClockCmd(RCC_APB2Periph_GPIOD, ENABLE); // to Enable the clock for Port D

GPIO_InitStructure.GPIO_Pin = GPIO_Pin_0; // Defines which Pin to configure
GPIO_InitStructure.GPIO_Mode = GPIO_Mode_Out_PP; // Defines Output Type
GPIO_InitStructure.GPIO_Speed = GPIO_Speed_50MHz; // Defines speed
GPIO_Init(GPIOD, &GPIO_InitStructure);

GPIO_InitStructure.GPIO_Pin = GPIO_Pin_1; // Defines which Pin to configure
GPIO_InitStructure.GPIO_Mode = GPIO_Mode_Out_OD; // Defines Output Type
GPIO_InitStructure.GPIO_Speed = GPIO_Speed_2MHz; // Defines speed
GPIO_Init(GPIOC, &GPIO_InitStructure);

}

Now, let us see which all functions are available for controlling the GPIO pins or port.

if you go through ch32v00x_gpio.h header file, you can see there following function which you will be using for GPIO output operations

Function names are self explainatory.

void     GPIO_SetBits(GPIO_TypeDef *GPIOx, uint16_t GPIO_Pin);
void     GPIO_ResetBits(GPIO_TypeDef *GPIOx, uint16_t GPIO_Pin);
void     GPIO_WriteBit(GPIO_TypeDef *GPIOx, uint16_t GPIO_Pin, BitAction BitVal);
void     GPIO_Write(GPIO_TypeDef *GPIOx, uint16_t PortVal);
void     GPIO_PinLockConfig(GPIO_TypeDef *GPIOx, uint16_t GPIO_Pin);

• GPIO_SetBits is used for setting the Pin High
• GPIO_ResetBits is used for setting the Pin Low
• GPIO_WriteBit is used when you want to SET and REST the pin with the same function
• GPIO_Write function is provided to set complete GPIO port, for example, if you have connected a 16×2 LCD display with 8 bit data port on Port D, you can use this function to set the data port which will set D0-7 pins with a single function call.
• GPIO_PinLockConfig this very interesting and special function, this helps you lock the pin so that accidently in other part of the configuration cannot be changed.

Hardware Circuit for LED Interface

Following circuit can be used for connecting the LED.

External oscillator is optional and only really required where you need high precision clock for timing of the interfaces like UART, Timer, PWM, etc.

External Reset Circuit is also not required if you use D7 as GPIO.

Programmer will be connected to 3.3V, GND and SWIO pins only.

CH32V003 Blinking LED Example

Now, let us see how we can blink an LED (connected on D0) with a delay of 500mSec so the LED will be ON for 500 mSec and OFF for 500 mSec. This is using GPIO_WriteBit function.

Delay_Ms function is available to give a block delay in milliseconds.

while(1)
{
    Delay_Ms(500);
    GPIO_WriteBit(GPIOD, GPIO_Pin_0, SET);
    Delay_Ms(500);
    GPIO_WriteBit(GPIOD, GPIO_Pin_0, RESET);
}

Now if we want to do the same with GPIO_SetBits and GPIO_RestBits function, we will have to write the code like this:

while(1)
{
    Delay_Ms(500);
    GPIO_SetBits(GPIOD, GPIO_Pin_0);
    Delay_Ms(500);
    GPIO_ResetBits(GPIOD, GPIO_Pin_0);
}

Complete code will be like this:

 * @brief   Initializes GPIOD.0
 *
 * @return  none
 */
void GPIOConfig(void)
{
    GPIO_InitTypeDef GPIO_InitStructure = {0};

    RCC_APB2PeriphClockCmd(RCC_APB2Periph_GPIOD, ENABLE);
    
    GPIO_InitStructure.GPIO_Pin = GPIO_Pin_0;
    GPIO_InitStructure.GPIO_Mode = GPIO_Mode_Out_PP;
    GPIO_InitStructure.GPIO_Speed = GPIO_Speed_50MHz;
    GPIO_Init(GPIOD, &GPIO_InitStructure);
}

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

    NVIC_PriorityGroupConfig(NVIC_PriorityGroup_2);
    SystemCoreClockUpdate(); // Configure MCU Clock HSI
    Delay_Init(); // 6mSec delay to allow clock to stabilize
    GPIOConfig(); // Configure the GPIO Pins

    while(1)
    {
        Delay_Ms(500);
        GPIO_SetBits(GPIOD, GPIO_Pin_0);
        Delay_Ms(500);
        GPIO_ResetBits(GPIOD, GPIO_Pin_0);
        
    }
}

Video show Blinking LED in action

Delay Function Time accuracy

In an experiment, I tried to check what is the accuracy of Delay_Ms() function, the code I use for testing was as shown below:

 while(1)
    {
        Delay_Ms(100);
        GPIO_SetBits(GPIOD, GPIO_Pin_4);
        Delay_Ms(100);
        GPIO_ResetBits(GPIOD, GPIO_Pin_4);
        
        Delay_Ms(100);
        GPIO_SetBits(GPIOD, GPIO_Pin_4);
        Delay_Ms(100);
        GPIO_ResetBits(GPIOD, GPIO_Pin_4);
        
        Delay_Ms(500);
        GPIO_SetBits(GPIOD, GPIO_Pin_4);
        Delay_Ms(500);
        GPIO_ResetBits(GPIOD, GPIO_Pin_4);

    }

I used Saleae Logic Analyzer for testing and here is the result. You can see in the waveform the delay time was quite accurate.

I would highly recommend to use Saleae Logic Analyzer for your digital timing analysis or debugging while working with various digital interfaces like UART, I2C, SPI, RS4

I hope you got a good understanding of the GPIO Out configuration and how to use it in your program.

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See also

1. Setting up the Development Environment for CH32V003: Compile and Run first example code
2. CH32V003: GPIO as Output
3. CH32V003: GPIO as Input (Polling / Interrupt)
4. CH32V003: UART Transmit / Receive data
5. CH32V003: PWM output with Frequency and Duty Cycle Control
6. CH32V003: ADC for analog signal measurement
7. CH32V003: I2C Interface
8. CH32V003: SPI Interface
9. CH32V003: Timer Interrupt
10. CH32V003: How to read 64-bit Unique ID

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I am currently working as an embedded systems design consultant and helping companies build custom embedded products, develop test automation solution for their PCB.

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