Comparison between hardware SPI and software analog SPI rate

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1、 Preface

This article USES the AT32F425 drive RC522 To test SPI1 Rate , About RC522 The detailed code operation of can be found in the post 【GD32L233C-START】 Hardware SPI1 drive RC522.

2、 About AT32F425 Of SPI

AT32F425 The series has at most 3 individual spi, This article USES the SPI1.

3、SPI1 The maximum rate of

SPI1 Hang on APB2 On the bus ,APB2 The maximum speed of the bus is 96MHz;
SPI The maximum rate of is fPCLK/2, namely 48Mhz.

4、 Code implementation

/*SPI1 :  
    PA4/CS  
    PA5/SCK    
    PA6/MISO   
    PA7/MOSI    
*/

（1） simulation SPI

#define SET_SPI_CS() gpio_bits_set(GPIOA, GPIO_PINS_4)
#define CLR_SPI_CS() gpio_bits_reset(GPIOA, GPIO_PINS_4) 

#define SET_SPI_SCLK() gpio_bits_set(GPIOA,GPIO_PINS_5)
#define CLR_SPI_SCLK() gpio_bits_reset(GPIOA,GPIO_PINS_5)//SCL=SCLK

#define SET_SPI_MOSI() gpio_bits_set(GPIOA,GPIO_PINS_7)
#define CLR_SPI_MOSI() gpio_bits_reset(GPIOA,GPIO_PINS_7)//SDO=MOSI

#define READ_SPI_MISO() gpio_input_data_bit_read(GPIOA,GPIO_PINS_6) //SDI=MISO

void SpiIoInit(void)
{
    	
	crm_periph_clock_enable(CRM_GPIOA_PERIPH_CLOCK, TRUE);

	gpio_init_type gpio_initstructure;
	
    /* configure the lcd gpio */
	gpio_initstructure.gpio_drive_strength = GPIO_DRIVE_STRENGTH_STRONGER;
	gpio_initstructure.gpio_out_type  = GPIO_OUTPUT_PUSH_PULL;
	gpio_initstructure.gpio_mode = GPIO_MODE_OUTPUT;
	gpio_initstructure.gpio_pins = GPIO_PINS_4|GPIO_PINS_5|GPIO_PINS_7;
	gpio_initstructure.gpio_pull = GPIO_PULL_NONE;
	gpio_init(GPIOA, &gpio_initstructure);
	
	gpio_bits_set(GPIOA,GPIO_PINS_4|GPIO_PINS_5|GPIO_PINS_7);
	
	gpio_initstructure.gpio_drive_strength = GPIO_DRIVE_STRENGTH_STRONGER;
	gpio_initstructure.gpio_out_type  = GPIO_OUTPUT_PUSH_PULL;
	gpio_initstructure.gpio_mode = GPIO_MODE_INPUT;
	gpio_initstructure.gpio_pins = GPIO_PINS_6;
	gpio_initstructure.gpio_pull = GPIO_PULL_NONE;
	gpio_init(GPIOA, &gpio_initstructure);
	
	gpio_bits_set(GPIOA,GPIO_PINS_6);
	
}

uint8_t  SPIWriteByte(uint8_t dat)
{
    
	uint16_t ret=0;

	u8 i;
	
	CLR_SPI_CS();
	for(i=0;i<8;i++)
	{
    			  
		if(dat&0x80)
		{
    
		   SET_SPI_MOSI();
		}
		else
		{
    
		   CLR_SPI_MOSI();
		}
		dat<<=1;
// delay_us(1);
	
		SET_SPI_SCLK();
		ret<<=1;
		
		if(READ_SPI_MISO())
		{
    
			ret+=1;
		}
// delay_us(1);
		CLR_SPI_SCLK();
	}
	SET_SPI_CS();

	return (ret&0x0ff);
}

（2） Hardware SPI

void SpiIoInit(void)
{
    	
	gpio_initstructure.gpio_out_type       = GPIO_OUTPUT_PUSH_PULL;
	gpio_initstructure.gpio_pull           = GPIO_PULL_UP;
	gpio_initstructure.gpio_mode           = GPIO_MODE_OUTPUT;
	gpio_initstructure.gpio_drive_strength = GPIO_DRIVE_STRENGTH_STRONGER;
	gpio_initstructure.gpio_pins = GPIO_PINS_4;
	gpio_init(GPIOA, &gpio_initstructure);
  
	gpio_pin_mux_config(GPIOA, GPIO_PINS_SOURCE5, GPIO_MUX_0);
	gpio_pin_mux_config(GPIOA, GPIO_PINS_SOURCE6, GPIO_MUX_0);
	gpio_pin_mux_config(GPIOA, GPIO_PINS_SOURCE7, GPIO_MUX_0);

	gpio_default_para_init(&gpio_initstructure);

	gpio_initstructure.gpio_out_type       = GPIO_OUTPUT_PUSH_PULL;
	gpio_initstructure.gpio_pull           = GPIO_PULL_DOWN;
	gpio_initstructure.gpio_mode           = GPIO_MODE_MUX;
	gpio_initstructure.gpio_drive_strength = GPIO_DRIVE_STRENGTH_STRONGER;
	gpio_initstructure.gpio_pins = GPIO_PINS_5;
	gpio_init(GPIOA, &gpio_initstructure);

	gpio_initstructure.gpio_out_type       = GPIO_OUTPUT_PUSH_PULL;
	gpio_initstructure.gpio_pull           = GPIO_PULL_UP;
	gpio_initstructure.gpio_mode           = GPIO_MODE_MUX;
	gpio_initstructure.gpio_drive_strength = GPIO_DRIVE_STRENGTH_STRONGER;
	gpio_initstructure.gpio_pins = GPIO_PINS_6;
	gpio_init(GPIOA, &gpio_initstructure);

	gpio_initstructure.gpio_out_type       = GPIO_OUTPUT_PUSH_PULL;
	gpio_initstructure.gpio_pull           = GPIO_PULL_UP;
	gpio_initstructure.gpio_mode           = GPIO_MODE_MUX;
	gpio_initstructure.gpio_drive_strength = GPIO_DRIVE_STRENGTH_STRONGER;
	gpio_initstructure.gpio_pins = GPIO_PINS_7;
	gpio_init(GPIOA, &gpio_initstructure);
	
	spi_init_type spi_init_struct;

	crm_periph_clock_enable(CRM_SPI1_PERIPH_CLOCK, TRUE);

	spi_default_para_init(&spi_init_struct);
	spi_init_struct.transmission_mode = SPI_TRANSMIT_FULL_DUPLEX;
	spi_init_struct.master_slave_mode = SPI_MODE_MASTER;
	spi_init_struct.mclk_freq_division = SPI_MCLK_DIV_8;
	spi_init_struct.first_bit_transmission = SPI_FIRST_BIT_MSB;
	spi_init_struct.frame_bit_num = SPI_FRAME_8BIT;
	spi_init_struct.clock_polarity = SPI_CLOCK_POLARITY_LOW;
	spi_init_struct.clock_phase = SPI_CLOCK_PHASE_1EDGE;
	spi_init_struct.cs_mode_selection = SPI_CS_SOFTWARE_MODE;
	spi_init(SPI1, &spi_init_struct);
	spi_enable(SPI1, TRUE);
}

uint8_t  SPIWriteByte(uint8_t dat)
{
    
	uint16_t ret=0;

    CLR_SPI_CS();
	while(spi_i2s_flag_get(SPI1, SPI_I2S_TDBE_FLAG) == RESET) {
    };
    spi_i2s_data_transmit(SPI1, dat);
		
    while(spi_i2s_flag_get(SPI1, SPI_I2S_RDBF_FLAG) == RESET) {
    };
    ret=spi_i2s_data_receive(SPI1);
    SET_SPI_CS();		
	return (ret&0x0ff);
}

Use hardware SPI When testing ,RC522 The maximum speed of can only reach 12MHZ, That is to say 8 frequency division , The rate is too high, which leads to communication failure .

5、 Rate measurement

Here, use an oscilloscope directly CLK Waveform of , Grasp the whole with logical analysis SPI Waveform of .

（1） simulation SPI


It can be seen that , Using simulation SPI The time is 1.8MHz, Grabbing with logic analyzer is also the result .

（2） Hardware SPI


It can be seen that , Use hardware SPI The time is 12MHz, Consistent with the software settings , Grabbing with logic analyzer is also the result .

Comprehensive comparative measurement , You can find , Hardware SPI The speed is much higher than that of software SPI, So in order to improve cpu Utilization ratio , Try to use hardware SPI.

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