使用beaglebone Black SPI在DIP203-6 LCD屏幕上显示字符

Question

我正在尝试使用beagle bone black SPI为我的DIP203-6 LCD写一个字符。当光标在正确位置闪烁时，我已初始化LCD屏幕。我面临的问题是在the data sheet中编写字符时，字符的写入需要10位，但spi只能占用8位。根据数据表中的命令，LCD的RS需要为1。我倾向于得到一些垃圾值。

在int main（）部分，最后您可以看到我正在使用主要上方的传递函数传输命令

#include <stdint.h>
#include <unistd.h>
#include <stdio.h>
#include <stdlib.h>
#include <getopt.h>
#include <fcntl.h>
#include <sys/ioctl.h>
#include <linux/types.h>
#include <linux/spi/spidev.h>

#define ARRAY_SIZE(a) (sizeof(a) / sizeof((a)[0]))
static void transfer(int fd, uint16_t* tx, uint8_t cs);
void init_display(int fd);

static void pabort(const char *s)
{
    perror(s);
    abort();
}

static const char *device = "/dev/spidev2.1";
static uint8_t mode=3;
static uint8_t bits = 8;
static uint32_t speed = 40000;
static uint16_t delay;

  //initialization of display

void init_display(int fd)
{
        int ret;
        uint16_t tx[] = {
                0x0F8, 0x000, 0x0C0,
                0x0F8, 0x060, 0x000,
                0x0F8, 0x060, 0x0C0,
                0x0FC, 0x090, 0x000,
                0x0FC, 0x000, 0x020,
                0x0FE, 0x000, 0x000,
                0x0F8, 0x000, 0x0C0,
                0x0F8, 0x0F0, 0x000,
                0x0F8, 0x080, 0x000,

        };

        for (ret=0; ret<27; ret++)
        {
                transfer(fd,&tx[ret], 0);
                  usleep(2000);
        }
}
static void transfer(int fd, uint16_t* tx, uint8_t cs){
    int ret;
    uint16_t rx[ARRAY_SIZE(tx)] = {0, };
    struct spi_ioc_transfer tr = {
        .tx_buf = (unsigned long)tx,
        .rx_buf = 0,
        .len = 1,
        .delay_usecs = delay,
        .speed_hz = speed,
        .bits_per_word = bits,
        .cs_change=cs,
    };
    printf("%u", cs);

    ret = ioctl(fd, SPI_IOC_MESSAGE(1), &tr);
    if (ret < 1)
        pabort("can't send spi message");

//  for (ret = 0; ret < ARRAY_SIZE(tx); ret++) {
    //  if (!(ret % 6))
        puts("");
    //  printf("%.2X ", rx[ret]);
    }
//  puts("");


static void print_usage(const char *prog)
{
    printf("Usage: %s [-DsbdlHOLC3]\n", prog);
    puts("  -D --device   device to use (default /dev/spidev1.1)\n"
         "  -s --speed    max speed (Hz)\n"
         "  -d --delay    delay (usec)\n"
         "  -b --bpw      bits per word \n"
         "  -l --loop     loopback\n"
         "  -H --cpha     clock phase\n"
         "  -O --cpol     clock polarity\n"
         "  -L --lsb      least significant bit first\n"
         "  -C --cs-high  chip select active high\n"
         "  -3 --3wire    SI/SO signals shared\n");
    exit(1);
}

static void parse_opts(int argc, char *argv[])
{
    while (1) {
        static const struct option lopts[] = {
            { "device",  1, 0, 'D' },
            { "speed",   1, 0, 's' },
            { "delay",   1, 0, 'd' },
            { "bpw",     1, 0, 'b' },
            { "loop",    0, 0, 'l' },
            { "cpha",    0, 0, 'H' },
            { "cpol",    0, 0, 'O' },
            { "lsb",     0, 0, 'L' },
            { "cs-high", 0, 0, 'C' },
            { "3wire",   0, 0, '3' },
            { "no-cs",   0, 0, 'N' },
            { "ready",   0, 0, 'R' },
            { NULL, 0, 0, 0 },
        };
        int c;

        c = getopt_long(argc, argv, "D:s:d:b:lHOLC3NR", lopts, 
NULL);

        if (c == -1)
            break;

        switch (c) {
        case 'D':
            device = optarg;
            break;
        case 's':
            speed = atoi(optarg);
            break;
        case 'd':
            delay = atoi(optarg);
            break;
        case 'b':
            bits = atoi(optarg);
            break;
        case 'l':
            mode |= SPI_LOOP;
            break;
        case 'H':
            mode |= SPI_CPHA;
            break;
        case 'O':
            mode |= SPI_CPOL;
            break;
        case 'L':
            mode |= SPI_LSB_FIRST;
            break;
        case 'C':
            mode |= SPI_CS_HIGH;
            break;
        case '3':
            mode |= SPI_3WIRE;
            break;
        case 'N':
            mode |= SPI_NO_CS;
            break;
        case 'R':
            mode |= SPI_READY;
            break;
        default:
            print_usage(argv[0]);
            break;
        }
    }
}

int main(int argc, char *argv[])
{
    int ret = 0;
    int fd;

    parse_opts(argc, argv);

    fd = open(device, O_RDWR);
    if (fd < 0)
        pabort("can't open device");

    /*
     * spi mode
     */
    ret = ioctl(fd, SPI_IOC_WR_MODE, &mode);
    if (ret == -1)
        pabort("can't set spi mode");

    ret = ioctl(fd, SPI_IOC_RD_MODE, &mode);
    if (ret == -1)
        pabort("can't get spi mode");

    /*
     * bits per word
     */
    ret = ioctl(fd, SPI_IOC_WR_BITS_PER_WORD, &bits);
    if (ret == -1)
        pabort("can't set bits per word");

    ret = ioctl(fd, SPI_IOC_RD_BITS_PER_WORD, &bits);
    if (ret == -1)
        pabort("can't get bits per word");

    /*
     * max speed hz
     */
    ret = ioctl(fd, SPI_IOC_WR_MAX_SPEED_HZ, &speed);
    if (ret == -1)
        pabort("can't set max speed hz");

    ret = ioctl(fd, SPI_IOC_RD_MAX_SPEED_HZ, &speed);
    if (ret == -1)
        pabort("can't get max speed hz");

    printf("spi mode: %d\n", mode);
    printf("bits per word: %d\n", bits);
    printf("max speed: %d Hz (%d KHz)\n", speed, speed/1000);

    init_display(fd);
       usleep(20000);
    uint16_t hl[]={0X38,0X0E,0X06,0XF8,0X30,0x50,0x02};
    trnsfer(fd,hl,0);

    close(fd);

    return ret;
}

Answer 1

您的LCD模块使用SSD1803控制器。根据the data sheet，您需要传输3个字节进行写操作。

第一个字节是一个起始字节，由5位“1”组成，后跟R / W，RS和结束位（“0”）。

接下来的2个字节是数据字节。低4位数据后跟4“0”。然后，高4位数据后跟4“0”。

• 第1个字节：“1”“1”“1”“1”“1”R / W（“0”）RS（“1”）“0”
• 第二个字节：D0 D1 D2 D3“0”“0”“0”“0”
• 查看住宅：D4 D5 D6 D7“0”“0”“0”“0”

数据手册中的图7-11说明了此操作。

此外，看起来你正在传递一个数组，但我认为传递函数只传输一个字节，因为.len = 1;。

struct spi_ioc_transfer tr = {
  .tx_buf = (unsigned long)tx,
  .rx_buf = 0,
  .len = 1, // <- HERE
  .delay_usecs = delay,
  .speed_hz = speed,
  .bits_per_word = bits,
  .cs_change=cs,
};

你想传输3个字节。您可以修改函数并根据数组的大小指定长度。或者，如果在传输之间保持CS较低，则可以遍历数组并逐个发送一个字节。