There are 4 available SPI controllers available. Each can be configured as a master or slave device.
In this tutorial we will briefly go over configuring the hardware & kernel followed by a C sample demonstrating some master & slave interaction.
Enabling SPI in the Linux Kernel
CONFIG_SPI=y
CONFIG_SPI_MASTER=y
CONFIG_SPI_SUNXI=y
CONFIG_SUNXI_SPI_NDMA=y
CONFIG_SPI_SPIDEV=y
CONFIG_SPI_SLAVE=y
Sample sys_config (script.bin)
[spi_board0]
modalias = "spidev"
max_speed_hz = 8000000
bus_num = 0
chip_select = 0
mode = 1
full_duplex = 0
manual_cs = 0
is_slave = 1
[spi_board1]
modalias = "spidev"
max_speed_hz = 8000000
bus_num = 1
chip_select = 0
mode = 1
full_duplex = 0
manual_cs = 0
[spi_board2]
modalias = "spidev"
max_speed_hz = 8000000
bus_num = 2
chip_select = 0
mode = 1
full_duplex = 0
manual_cs = 0
[spi_devices]
spi_dev_num = 3
[spi0_para]
spi_used = 1
spi_cs_bitmap = 1
spi_cs0 = port:PI10<2><default><default><default>
spi_cs1 =
spi_sclk = port:PI11<2><default><default><default>
spi_mosi = port:PI12<2><default><default><default>
spi_miso = port:PI13<2><default><default><default>
[spi1_para]
spi_used = 1
spi_cs_bitmap = 1
spi_cs0 = port:PI16<2><default><default><default>
spi_cs1 =
spi_sclk = port:PI17<2><default><default><default>
spi_mosi = port:PI18<2><default><default><default>
spi_miso = port:PI19<2><default><default><default>
[spi2_para]
spi_used = 1
spi_cs_bitmap = 1
spi_cs0 = port:PB14<2><default><default><default>
spi_cs1 =
spi_sclk = port:PB15<2><default><default><default>
spi_mosi = port:PB16<2><default><default><default>
spi_miso = port:PB17<2><default><default><default>
[spi3_para]
spi_used = 0
spi_cs_bitmap = 1
spi_cs0 = port:PA05<3><default><default><default>
spi_cs1 = port:PA09<3><default><default><default>
spi_sclk = port:PA06<3><default><default><default>
spi_mosi = port:PA07<3><default><default><default>
spi_miso = port:PA08<3><default><default><default>
Note: An equivelnt sample device tree source (DTS) for use with newer versions of the kernel will be made available soon.
Check your dmesg to make sure the devices are properly configured.
root@awsom:~# dmesg | grep spi
[ 1.024251] [spi-inf] Found 3 spi devices in config files
[ 1.031558] [spi-inf] boards num modalias max_spd_hz bus_num cs mode slave
[ 1.042494] [spi-inf] 0 spidev 8000000 0 0 0x1 Y
[ 1.053388] [spi-inf] 1 spidev 8000000 1 0 0x1 N
[ 1.064281] [spi-inf] 2 spidev 8000000 2 0 0x1 N
[ 1.069217] [spi-inf] sunxi_spi_probe: spi0 dma type: normal
[ 1.077790] [spi-inf] sunxi_spi_set_mclk: spi0 source = sdram_pll_p, src_clk = 408000000, mclk 81600000
[ 1.084932] [spi-inf] allwinners SoC SPI Driver loaded for Bus SPI-0 as slave device
[ 1.089598] [spi-inf] sunxi_spi_probe: spi1 dma type: normal
[ 1.093173] [spi-inf] bus num = 1, spi used = 1
[ 1.097611] [spi-inf] sunxi_spi_probe: spi1 cs bitmap: 0x1
[ 1.106160] [spi-inf] sunxi_spi_set_mclk: spi1 source = sdram_pll_p, src_clk = 408000000, mclk 81600000
[ 1.112032] sun7i-spi sun7i-spi.1: master is unqueued, this is deprecated
[ 1.121001] [spi-inf] sunxi_spi_probe: reuuimlla's SoC SPI Driver loaded for Bus SPI1 with 2 Slaves at most
[ 1.130410] [spi-inf] sunxi_spi_probe: spi1 driver probe succeed, base f00d6000, irq 43, dma_id_rx 25, dma_id_tx 25
[ 1.135058] [spi-inf] sunxi_spi_probe: spi2 dma type: normal
[ 1.138645] [spi-inf] bus num = 2, spi used = 1
[ 1.143084] [spi-inf] sunxi_spi_probe: spi2 cs bitmap: 0x1
[ 1.151593] [spi-inf] sunxi_spi_set_mclk: spi2 source = sdram_pll_p, src_clk = 408000000, mclk 81600000
[ 1.157454] sun7i-spi sun7i-spi.2: master is unqueued, this is deprecated
[ 1.166402] [spi-inf] sunxi_spi_probe: reuuimlla's SoC SPI Driver loaded for Bus SPI2 with 2 Slaves at most
[ 1.175808] [spi-inf] sunxi_spi_probe: spi2 driver probe succeed, base f00d8000, irq 44, dma_id_rx 26, dma_id_tx 26
Sample C program demonstrating Master & Slave
compile with -DSLAVE to compile as slave. You will also need to include spidev.h or equivalent prototypes in your build path.
gcc spi.c -o master gcc spi.c -DSLAVE -o slave
./master <dev> <speed> <len> <udelay>
./slave <dev> <speed> <len>
#include <stdint.h>
#include <unistd.h>
#include <sys/time.h>
#include <signal.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <getopt.h>
#include <fcntl.h>
#include <sys/ioctl.h>
#include <linux/types.h>
//#include <linux/spi/spidev.h>
#include "spidev.h"
//#define DEBUG
char spi_dev[16];
long speed=50000;
long udelay=0;
struct spi_ioc_transfer xfer[2];
struct timeval start, finish;
long msec;
int file;
unsigned short crc16(unsigned char* data_p, unsigned char length){
unsigned char x;
unsigned short crc = 0xFFFF;
while (length--){
x = crc >> 8 ^ *data_p++;
x ^= x>>4;
crc = (crc << 8) ^ ((unsigned short)(x << 12)) ^
((unsigned short)(x <<5)) ^ ((unsigned short)x);
}
return crc;
}
long timevaldiff(struct timeval *starttime, struct timeval *finishtime)
{
long msec;
msec=(finishtime->tv_sec-starttime->tv_sec)*1000;
msec+=(finishtime->tv_usec-starttime->tv_usec)/1000;
return msec;
}
int spi_init(char filename[40])
{
int file;
__u8 mode, lsb, bits;
__u32 speed=speed;
if ((file = open(filename,O_RDWR)) < 0)
{
printf("Failed to open the bus.");
/* ERROR HANDLING; you can check errno to see what went wrong */
exit(1);
}
/*multiple modes:
mode |= SPI_LOOP;
mode |= SPI_CPHA;
mode |= SPI_CPOL;
mode |= SPI_LSB_FIRST;
mode |= SPI_CS_HIGH;
mode |= SPI_3WIRE;
mode |= SPI_NO_CS;
mode |= SPI_READY;
if (ioctl(file, SPI_IOC_WR_MODE, &mode)<0) {
perror("can't set spi mode");
return;
}
*/
if (ioctl(file, SPI_IOC_RD_MODE, &mode) < 0)
{
perror("SPI rd_mode");
return;
}
if (ioctl(file, SPI_IOC_RD_LSB_FIRST, &lsb) < 0)
{
perror("SPI rd_lsb_fist");
return;
}
if (ioctl(file, SPI_IOC_RD_BITS_PER_WORD, &bits) < 0)
{
perror("SPI bits_per_word");
return;
}
if (ioctl(file, SPI_IOC_RD_MAX_SPEED_HZ, &speed) < 0)
{
perror("SPI max_speed_hz");
return;
}
printf("%s: spi mode %d, %d bits %sper word, %d Hz max\n",
filename, mode, bits, lsb ? "(lsb first) " : "", speed);
xfer[0].cs_change = 0; // Keep CS activated
xfer[0].delay_usecs = udelay;
xfer[0].speed_hz = speed;
xfer[0].bits_per_word = 8; // 8-bites per word only
xfer[1].cs_change = 0;
xfer[1].delay_usecs = 0;
xfer[1].speed_hz = speed;
xfer[1].bits_per_word = 8;
return file;
}
int spi_read(int add1,int add2,int nbytes,char* buffer,int file)
{
static char cmd[3];
int status;
memset(buffer, 0, nbytes);
cmd[0] = 0x01;
cmd[1] = add1;
cmd[2] = add2;
xfer[0].tx_buf = (unsigned long)cmd;
xfer[0].len = 3; /* Length of command to write*/
xfer[1].rx_buf = (unsigned long) buffer;
xfer[1].len = nbytes; /* Length of Data to read */
status = ioctl(file, SPI_IOC_MESSAGE(2), xfer);
if (status < 0)
{
perror("SPI_IOC_MESSAGE");
}
return status;
}
int spi_slave_read(int nbytes,char* buffer, int file)
{
int status;
memset(buffer, 0, nbytes);
xfer[0].rx_buf = (unsigned long) buffer;
xfer[0].len = nbytes; /* Length of Data to read */
status = ioctl(file, SPI_IOC_MESSAGE(1), xfer);
if (status < 0)
{
perror("SPI_IOC_MESSAGE");
}
return status;
}
void spi_write(int nbytes,char* buffer,int file)
{
int status;
xfer[0].tx_buf = (unsigned long)buffer;
xfer[0].len = nbytes; /* Length of command to write */
status = ioctl(file, SPI_IOC_MESSAGE(1), xfer);
if (status < 0)
{
perror("SPI_IOC_MESSAGE");
return;
}
}
void dump(char *buffer, int len){
int x;
for(x=0; x<len; x++){
printf("0x%X ",*(buffer+x));
}
printf("\n");
}
void quit(int sig)
{
printf("Closing...\n");
close(file);
exit(0);
}
main ( int argc, char **argv ) {
int x, y, len,status;
long frame, last_frame, good, bad;
unsigned short crc;
char *rd,*wr;
signal (SIGINT, quit);
if(argc!=4 && argc!=5){
#ifdef SLAVE
printf("Usage: ./slave <dev> <speed> <len>\n\t" \
"./slave 2 5000000 64\n");
#else
printf("Usage: ./master <dev> <speed> <len> <udelay>\n\t" \
"./master 1 5000000 64 100\n");
#endif
exit(0);
}
good=bad=0;
frame=1;
sprintf(spi_dev,"/dev/spidev%s.0",argv[1]);
speed=atoi(argv[2]);
len= atoi(argv[3]);
if(argc==5)
udelay=atoi(argv[4]);
#ifdef SLAVE /* Run as Slave */
rd=(char*)malloc(3);
wr=(char*)malloc(len);
printf("Slave: %s speed=%s len=%s\n", spi_dev, argv[2], argv[3]);
file=spi_init(spi_dev);
while(1){
status=spi_slave_read(3,rd,file);
if(*rd==0x01){
frame=(*(rd+1)+(*(rd+2)<<8));
*(wr)=frame&0xff;
*(wr+1)=(frame>>8)&0xff;
*(wr+2)=3;
*(wr+3)=4;
for(y=4; y<len-2; y++)
*(wr+y)=(frame%0xff);
crc=crc16(wr,len-2);
*(wr+(len-1))=crc&0xff;
*(wr+(len-2))=(crc>>8)&0xff;
#ifdef DEBUG
dump(wr,10);
printf("\n");
#endif
spi_write(len,wr,file);
if(last_frame==frame)
printf("Slave resend frame %ld %d bytes \n", frame, len);
}
last_frame=frame;
}
#else /* Run as Master */
wr=(char*)malloc(3);
rd=(char*)malloc(len);
printf("Master: %s speed=%s len=%s\n", spi_dev, argv[2], argv[3]);
x=0;
file=spi_init(spi_dev);
gettimeofday(&start, NULL);
while(1){
//gettimeofday(&start, NULL);
spi_read(frame&0xff, ((frame>>8)&0xff), len, rd, file);
if(*(rd+2)==3 && *(rd+3)==4){
crc=crc16(rd,len);
if(crc==0){
good++;
frame++;
}else{
bad++;
printf("invalid crc %X for frame %ld. retry!\n", crc, frame);
}
#ifdef DEBUG
printf("Master Read ");
dump(rd,10);
#endif
gettimeofday(&finish, NULL);
msec = timevaldiff(&start, &finish);
if(frame%1000==0) /* show update every 1K frames */
printf("Master read %ld kb in %ldms %ld/%ld\n",
(len*frame)/1000, msec, good, bad);
}else{
bad++;
#ifdef DEBUG
printf("Invalid data!\n");
dump(rd,10);
#endif
}
}
#endif
return 0;
}
