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ZYNQ_FPGA_SPI通信协议多种实现方式

文章目录


本文记录一下在使用AD9363中的SPI通信问题，同时针对在ZYNQ系列开发板上实现SPI的方法做一个总结。
ZYNQ系列包含了PL端和PS端，因为本科阶段有一定的ARM的开发经验，便想着学习一下ZYNQ的PS端的基础开发。于是，有了下文。
在这里插入图片描述
Zynq-7000 SOC的系统框图如上，PL自然是使用HDL语言来开发，也是FPGA开发的老本行了。观察PS端的资源，可以看到其外已经包含了SPI控制器，同时还有丰富的GPIO。联想到ARM开发中常说的软件SPI和硬件SPI，便可以从中入手。后面还会介绍使用Xilinx的IP核在实现SPI。
关于SPI的具体细节就不介绍了，直接看需求。
在这里插入图片描述
从AD9363的SPI Configuration寄存器的默认值0x00，可知其上电默认采用MSB first的4-wire SPI。
在这里插入图片描述
指令字的第15位决定在指令字节写入之后是读数据传输还是写数据传输。逻辑高表示写操作；逻辑零表示读操作。
指令字的位[14:12] 指定在I/O 操作的阶段2 期间传输的字节数，简单起见，直接默认NB2-NB0 = b000。
官方手册中的读写时序如下图。可知其CPOL = 0，即SPI_SCLK空闲为低电平；CPHA = 1，即在SPI_SCLK第二个跳变沿采样。
在这里插入图片描述

PL

源代码（来自Alinx FL9267参考例程）：
该模块完成了SPI单个字节的传输功能，可设置时钟分频、时钟极性、时钟相位。使用时，可以直接修改程序将该模块扩展至三个字节；也可以再写一个模块，完成三个字节读写的控制。

module spi_master
(
	input                       sys_clk,	
	input                       rst,
	output                      nCS,       //chip select (SPI mode) 
	output                      DCLK,      //spi clock
	output                      MOSI,      //spi data output
	input                       MISO,      //spi input
	input                       CPOL,
	input                       CPHA,
	input                       nCS_ctrl,
	input[15:0]                 clk_div,
	input                       wr_req,
	output                      wr_ack,
	input[7:0]                  data_in,
	output[7:0]                 data_out
);
localparam                   IDLE            = 0;
localparam                   DCLK_EDGE       = 1;
localparam                   DCLK_IDLE       = 2;
localparam                   ACK             = 3;
localparam                   LAST_HALF_CYCLE = 4;
localparam                   ACK_WAIT        = 5;
reg                          DCLK_reg;
reg[7:0]                     MOSI_shift;
reg[7:0]                     MISO_shift;
reg[2:0]                     state;
reg[2:0]                     next_state;
reg [15:0]                   clk_cnt;
reg[4:0]                     clk_edge_cnt;
assign MOSI = MOSI_shift[7];
assign DCLK = DCLK_reg;
assign data_out = MISO_shift;
assign wr_ack = (state == ACK);
assign nCS = nCS_ctrl;
always@(posedge sys_clk or posedge rst)
begin
	if(rst)
		state <= IDLE;
	else
		state <= next_state;
end

always@(*)
begin
	case(state)
		IDLE:
			if(wr_req == 1'b1)
				next_state <= DCLK_IDLE;
			else
				next_state <= IDLE;
		DCLK_IDLE:
			//half a SPI clock cycle produces a clock edge
			if(clk_cnt == clk_div)
				next_state <= DCLK_EDGE;
			else
				next_state <= DCLK_IDLE;
		DCLK_EDGE:
			//a SPI byte with a total of 16 clock edges
			if(clk_edge_cnt == 5'd15)
				next_state <= LAST_HALF_CYCLE;
			else
				next_state <= DCLK_IDLE;
		//this is the last data edge		
		LAST_HALF_CYCLE:
			if(clk_cnt == clk_div)
				next_state <= ACK;
			else
				next_state <= LAST_HALF_CYCLE; 
		//send one byte complete		
		ACK:
			next_state <= ACK_WAIT;
		//wait for one clock cycle, to ensure that the cancel request signal
		ACK_WAIT:
			next_state <= IDLE;
		default:
			next_state <= IDLE;
	endcase
end

always@(posedge sys_clk or posedge rst)
begin
	if(rst)
		DCLK_reg <= 1'b0;
	else if(state == IDLE)
		DCLK_reg <= CPOL;
	else if(state == DCLK_EDGE)
		DCLK_reg <= ~DCLK_reg;//SPI clock edge
end
//SPI clock wait counter
always@(posedge sys_clk or posedge rst)
begin
	if(rst)
		clk_cnt <= 16'd0;
	else if(state == DCLK_IDLE || state == LAST_HALF_CYCLE) 
		clk_cnt <= clk_cnt + 16'd1;
	else
		clk_cnt <= 16'd0;
end
//SPI clock edge counter
always@(posedge sys_clk or posedge rst)
begin
	if(rst)
		clk_edge_cnt <= 5'd0;
	else if(state == DCLK_EDGE)
		clk_edge_cnt <= clk_edge_cnt + 5'd1;
	else if(state == IDLE)
		clk_edge_cnt <= 5'd0;
end
//SPI data output
always@(posedge sys_clk or posedge rst)
begin
	if(rst)
		MOSI_shift <= 8'd0;
	else if(state == IDLE && wr_req)
		MOSI_shift <= data_in;
	else if(state == DCLK_EDGE)
		if(CPHA == 1'b0 && clk_edge_cnt[0] == 1'b1)
			MOSI_shift <= {MOSI_shift[6:0],MOSI_shift[7]};
		else if(CPHA == 1'b1 && (clk_edge_cnt != 5'd0 && clk_edge_cnt[0] == 1'b0))
			MOSI_shift <= {MOSI_shift[6:0],MOSI_shift[7]};
end
//SPI data input
always@(posedge sys_clk or posedge rst)
begin
	if(rst)
		MISO_shift <= 8'd0;
	else if(state == IDLE && wr_req)
		MISO_shift <= 8'h00;
	else if(state == DCLK_EDGE)
		if(CPHA == 1'b0 && clk_edge_cnt[0] == 1'b0)
			MISO_shift <= {MISO_shift[6:0],MISO};
		else if(CPHA == 1'b1 && (clk_edge_cnt[0] == 1'b1))
			MISO_shift <= {MISO_shift[6:0],MISO};
end
endmodule

仿真结果：
在这里插入图片描述

PS

在这里插入图片描述
ZYNQ-7000共有54个MIO引脚，其引脚是固定的；还有64个EMIO接口，可以通过修改约束文件连接到PL端的引脚。

SPI

ZYNQ-7000 SOC中SPI 控制器的特性如下。
在这里插入图片描述
值得注意的是，SPI控制器的总线可以连接到MIO引脚，也可以连接到EMIO接口，但是前者的SCLK最大速率可达到50 MHz，后者SCLK速率最高支持25 MHz。
Vivado Block Diagram中的配置如下。
在ZYNQ7 Processing System IP核中勾选SPI0，并根据开发板原理图选择IO，可选固定MIO或EMIO。其他使用PS端的基本配置和建立工程步骤就不详细展开了。
在这里插入图片描述
ad936x_spi.c

#include "ad936x_spi.h"

XSpiPs_Config	*spi_config;
XSpiPs			spi_instance;

int32_t spi_init(uint32_t device_id, uint8_t  clk_pha, uint8_t  clk_pol)
{
	uint32_t base_addr	 = 0;
	uint32_t spi_options = 0;
	spi_config = XSpiPs_LookupConfig(device_id);
	base_addr = spi_config->BaseAddress;

	XSpiPs_CfgInitialize(&spi_instance, spi_config, base_addr);

	spi_options = XSPIPS_MASTER_OPTION |
		      (clk_pol ? XSPIPS_CLK_ACTIVE_LOW_OPTION : 0) |
		      (clk_pha ? XSPIPS_CLK_PHASE_1_OPTION : 0) |
		      XSPIPS_FORCE_SSELECT_OPTION;

	XSpiPs_SetOptions(&spi_instance, spi_options);
	XSpiPs_SetClkPrescaler(&spi_instance, XSPIPS_CLK_PRESCALE_32);
	return 0;
}

int32_t spi_read(uint8_t *data, uint8_t bytes_number)
{
	XSpiPs_SetSlaveSelect(&spi_instance, 0);//spi0
	XSpiPs_PolledTransfer(&spi_instance, data, data, bytes_number);
	return 0;
}

int spi_write_then_read(unsigned char *txbuf, unsigned n_tx, unsigned char *rxbuf, unsigned n_rx)
{
	uint8_t buffer[20] = {0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
			      0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
			      0x00, 0x00, 0x00, 0x00
			     };
	uint8_t byte;

	for(byte = 0; byte < n_tx; byte++) {
		buffer[byte] = (unsigned char)txbuf[byte];
	}
	spi_read(buffer, n_tx + n_rx);
	for(byte = n_tx; byte < n_tx + n_rx; byte++) {
		rxbuf[byte - n_tx] = buffer[byte];
	}
	return 0;
}

uint8_t ad936x_spi_read(uint16_t addr)
{
	uint8_t txbuf[2];
	uint8_t rxbuf[1];
	uint8_t addr_msb = addr>>8;
	uint8_t addr_lsb = (uint8_t)addr;
	txbuf[0] = 0x7F & addr_msb;
	txbuf[1] = addr_lsb;
	spi_write_then_read(txbuf, 2, rxbuf, 1);
	return rxbuf[0];
}

void ad936x_spi_write(uint16_t addr, uint8_t data)
{
	uint8_t txbuf[3];
	uint8_t addr_msb = addr>>8;
	uint8_t addr_lsb = (uint8_t)addr;
	txbuf[0] = 0x80|addr_msb;
	txbuf[1] = addr_lsb;
	txbuf[2] = data;
	spi_write_then_read(txbuf, 3, NULL, 0);
}

ad936x_spi.h

#ifndef SRC_AD936X_SPI_H_
#define SRC_AD936X_SPI_H_

#include <stdint.h>
#include "stdio.h"
#include "xparameters.h"
#include "xspips.h"
#include "sleep.h"

#define SPI_DEVICE_ID	XPAR_PS7_SPI_0_DEVICE_ID

int32_t spi_init(uint32_t device_id, uint8_t  clk_pha, uint8_t  clk_pol);
int32_t spi_read(uint8_t *data, uint8_t bytes_number);
int spi_write_then_read(unsigned char *txbuf, unsigned n_tx, unsigned char *rxbuf, unsigned n_rx);
uint8_t ad936x_spi_read(uint16_t addr);
void ad936x_spi_write(uint16_t addr, uint8_t data);

#endif /* SRC_AD936X_SPI_H_ */

GPIO

ZYNQ-7000 SOC中GPIO的特性和框图如下。
在这里插入图片描述在这里插入图片描述
在ZYNQ7 Processing System IP核中勾选GPIO，其IO默认MIO，若想使用EMIO连接到PL的引脚，可勾选EMIOGPIO(Width)，并选择宽度，即需要使用多少个引脚。
在这里插入图片描述

用软件方式模拟实现SPI，只需要知道GPIO是如何输入输出的。
只给出初始化函数和GPIO输入输出操作函数，其他程序段参考下一节AXI_GPIO的内容。

#define GPIO_DEVICE_ID	XPAR_PS7_GPIO_0_DEVICE_ID
//MIO 0-53
#define MIO_LED 15
//EMIO 54-117
#define SPI_SCLK_Pins 54
#define SPI_MOSI_Pins 55
#define SPI_MISO_Pins 56
#define SPI_CS_Pins 57
#define RESET_Pins 58

XGpioPs_Config	*gpio_config;
XGpioPs			gpio_instance;

void gpio_init(uint32_t device_id)
{
	gpio_config = XGpioPs_LookupConfig(device_id);
	XGpioPs_CfgInitialize(&gpio_instance, gpio_config, gpio_config->BaseAddr);
	
	gpio_direction(MIO_LED, 1);
	gpio_direction(SPI_SCLK_Pins, 1);
	gpio_direction(SPI_MOSI_Pins, 1);
	gpio_direction(SPI_MISO_Pins, 0);
	gpio_direction(SPI_CS_Pins, 1);
	gpio_direction(RESET_Pins, 1);

	gpio_set_value(GPIO_RESET, 0);
	gpio_set_value(STA_LED, 0);
}

void gpio_direction(uint8_t pin, uint8_t direction)
{   //0 input, 1 output
	XGpioPs_SetDirectionPin(&gpio_instance, pin, direction);
	XGpioPs_SetOutputEnablePin(&gpio_instance, pin, 1);
}

void gpio_set_value(uint8_t pin, uint8_t value)
{
	XGpioPs_WritePin(&gpio_instance, pin, value);
}

uint8_t gpio_get_value(uint8_t pin)
{
	return (uint8_t)XGpioPs_ReadPin(&gpio_instance, pin);
}

AXI-GPIO

AXI-GPIO IP核可以说PS端GPIO的拓展，可以直接编写HDL程序控制该IP核，这里只讲解如何在PS端通过C语言程序控制，其本质也是对AXI总线的寄存器的读写。
使用AXI_GPIO的难点是如何控制将单个引脚的控制转换成AXI总线的地址读写操作。

#define SPI_SCLK_H  XGpio_DiscreteWrite(&axi_gpio1_inst, 1, XGpio_DiscreteRead(&axi_gpio1_inst, 1)|(0x0001<<SPI_SCLK_Pins))
#define SPI_SCLK_L  XGpio_DiscreteWrite(&axi_gpio1_inst, 1, XGpio_DiscreteRead(&axi_gpio1_inst, 1)&(~(0x0001<<SPI_SCLK_Pins)))
#define SPI_MOSI_H  XGpio_DiscreteWrite(&axi_gpio1_inst, 1, XGpio_DiscreteRead(&axi_gpio1_inst, 1)|(0x0001<<SPI_MOSI_Pins))
#define SPI_MOSI_L  XGpio_DiscreteWrite(&axi_gpio1_inst, 1, XGpio_DiscreteRead(&axi_gpio1_inst, 1)&(~(0x0001<<SPI_MOSI_Pins)))
#define SPI_CS_H    XGpio_DiscreteWrite(&axi_gpio1_inst, 1, XGpio_DiscreteRead(&axi_gpio1_inst, 1)|(0x0001<<SPI_CS_Pins))
#define SPI_CS_L    XGpio_DiscreteWrite(&axi_gpio1_inst, 1, XGpio_DiscreteRead(&axi_gpio1_inst, 1)&(~(0x0001<<SPI_CS_Pins)))
#define RESET_H     XGpio_DiscreteWrite(&axi_gpio1_inst, 1, XGpio_DiscreteRead(&axi_gpio1_inst, 1)|(0x0001<<RESET_Pins))
#define RESET_L     XGpio_DiscreteWrite(&axi_gpio1_inst, 1, XGpio_DiscreteRead(&axi_gpio1_inst, 1)&(~(0x0001<<RESET_Pins)))

Vivado Block Diagram如下：
在这里插入图片描述
ad936x_spi.c

#include "stdio.h"
#include "xparameters.h"
#include "xgpiops.h"
#include "xgpio.h"
#include "ad9363_spi.h"

XGpioPs gpiops_inst; //PS 端 GPIO 驱动实例
XGpioPs_Config *gpiops_cfg_ptr; //PS 端 GPIO 配置信息
XGpio axi_gpio1_inst; //PL 端 AXI GPIO1 驱动实例
XGpio axi_gpio2_inst; //PL 端 AXI GPIO2 驱动实例

void PS_AXI_GPIO_Init(void)
{
	//初始化 PS GPIO
	gpiops_cfg_ptr = XGpioPs_LookupConfig(GPIOPS_ID);
	XGpioPs_CfgInitialize(&gpiops_inst, gpiops_cfg_ptr, gpiops_cfg_ptr->BaseAddr);

	//初始化 PL AXI_GPIO
	XGpio_Initialize(&axi_gpio1_inst, AXI_GPIO_ID);
	XGpio_Initialize(&axi_gpio2_inst, AXI_GPIO_ID);

	//配置 PS GPIO
	XGpioPs_SetDirectionPin(&gpiops_inst, MIO_LED, 1); //设置 PS GPIO 为输出
	XGpioPs_SetOutputEnablePin(&gpiops_inst, MIO_LED, 1); //使能 LED 输出
	PS_LED_H;

	//配置PL AXI_GPIO
	XGpio_SetDataDirection(&axi_gpio1_inst, 1, 0); //设置 AXI GPIO 通道 1 为输出
	XGpio_SetDataDirection(&axi_gpio2_inst, 2, 1); //设置 AXI GPIO 通道 2 为输入
	SPI_SCLK_L;
	SPI_MOSI_L;
	SPI_CS_H;
	RESET_H;
}

void ad9363_SPI_Write(u16 addr, u8 data)
{
	SPI_CS_L;
	ad9363_SPI_Write_Byte((u8)(addr>>8)+0x80);
	ad9363_SPI_Write_Byte((u8)(addr));
	ad9363_SPI_Write_Byte(data);
	SPI_CS_H;
	SPI_MOSI_L;
}
void ad9363_SPI_Write_Byte(u8 wdata)
{
	u8 i = 0;
	for( i = 0; i< 8; i++){
		SPI_SCLK_H;
		if(wdata&0x80)
			SPI_MOSI_H;
		else
			SPI_MOSI_L;
		SPI_SCLK_L;
		SPI_MOSI_L;
		wdata <<= 1;
	}
}
u8 ad9363_SPI_Read(u16 addr)
{
	u8 rdata;
	SPI_CS_L;
	ad9363_SPI_Write_Byte((u8)(addr>>8));
	ad9363_SPI_Write_Byte((u8)(addr));
	rdata = ad9363_SPI_Read_Byte();
	SPI_CS_H;
	return rdata;
}
u8 ad9363_SPI_Read_Byte(void)
{
	u8 i;
	u8 rdata;
	for(i = 0; i<8; i++){
		SPI_SCLK_H;
		SPI_SCLK_L;
		if(XGpio_DiscreteRead(&axi_gpio2_inst, 2)&0x00001)
			rdata |= 0x80>>i;
	}
	return rdata;
}

void ps_LED(u8 status)
{
	if(status)
		PS_LED_H;
	else
		PS_LED_L;
}

ad936x_spi.h

#ifndef SRC_AD9363_SPI_AD9363_SPI_H_
#define SRC_AD9363_SPI_AD9363_SPI_H_

#include "stdio.h"
#include "xparameters.h"
#include "xgpiops.h"
#include "xgpio.h"

#define GPIOPS_ID    XPAR_XGPIOPS_0_DEVICE_ID  //PS 端 GPIO 器件 ID
#define AXI_GPIO_ID  XPAR_AXI_GPIO_0_DEVICE_ID //PL 端 AXI GPIO 器件 ID

//PS GPIO
#define MIO_LED 15 //PS LED 连接到 MIO0
//Channel 1 输出
#define SPI_SCLK_Pins 0 //PL SPI SCLK  GPIO 通道1
#define SPI_MOSI_Pins 1
#define SPI_CS_Pins 2
#define RESET_Pins 3
//Channel 2 输入
#define SPI_MISO_Pins 1

//PS GPIO 输出
#define PS_LED_H    XGpioPs_WritePin(&gpiops_inst, MIO_LED, 1)
#define PS_LED_L    XGpioPs_WritePin(&gpiops_inst, MIO_LED, 0)

//通道1 GPIO 输出
#define SPI_SCLK_H  XGpio_DiscreteWrite(&axi_gpio1_inst, 1, XGpio_DiscreteRead(&axi_gpio1_inst, 1)|(0x0001<<SPI_SCLK_Pins))
#define SPI_SCLK_L  XGpio_DiscreteWrite(&axi_gpio1_inst, 1, XGpio_DiscreteRead(&axi_gpio1_inst, 1)&(~(0x0001<<SPI_SCLK_Pins)))
#define SPI_MOSI_H  XGpio_DiscreteWrite(&axi_gpio1_inst, 1, XGpio_DiscreteRead(&axi_gpio1_inst, 1)|(0x0001<<SPI_MOSI_Pins))
#define SPI_MOSI_L  XGpio_DiscreteWrite(&axi_gpio1_inst, 1, XGpio_DiscreteRead(&axi_gpio1_inst, 1)&(~(0x0001<<SPI_MOSI_Pins)))
#define SPI_CS_H    XGpio_DiscreteWrite(&axi_gpio1_inst, 1, XGpio_DiscreteRead(&axi_gpio1_inst, 1)|(0x0001<<SPI_CS_Pins))
#define SPI_CS_L    XGpio_DiscreteWrite(&axi_gpio1_inst, 1, XGpio_DiscreteRead(&axi_gpio1_inst, 1)&(~(0x0001<<SPI_CS_Pins)))
#define RESET_H     XGpio_DiscreteWrite(&axi_gpio1_inst, 1, XGpio_DiscreteRead(&axi_gpio1_inst, 1)|(0x0001<<RESET_Pins))
#define RESET_L     XGpio_DiscreteWrite(&axi_gpio1_inst, 1, XGpio_DiscreteRead(&axi_gpio1_inst, 1)&(~(0x0001<<RESET_Pins)))

//通道2 GPIO 输入
//#define SPI_MISO_H  XGpio_DiscreteWrite(&axi_gpio2_inst, 2, XGpio_DiscreteRead(&axi_gpio2_inst, 2)|(0x0001<<SPI_MISO_Pins))
//#define SPI_MISO_L  XGpio_DiscreteWrite(&axi_gpio2_inst, 2, XGpio_DiscreteRead(&axi_gpio2_inst, 2)&(~(0x0001<<SPI_MISO_Pins)))

void PS_AXI_GPIO_Init(void);
void ad9363_SPI_Write(u16 addr, u8 data);
void ad9363_SPI_Write_Byte(u8 wdata);
u8 ad9363_SPI_Read(u16 addr);
u8 ad9363_SPI_Read_Byte(void);
void ps_LED(u8);

#endif /* SRC_AD9363_SPI_AD9363_SPI_H_ */

AXI-Quad-SPI

在这里插入图片描述
Vivado AXI Quad SPI

悦读

道可道，非常道；名可名，非常名。 无名，天地之始，有名，万物之母。 故常无欲，以观其妙，常有欲，以观其徼。 此两者，同出而异名，同谓之玄，玄之又玄，众妙之门。

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