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问题:

ARM:通过UART读取modbus数据失败

元望
2023-03-14

我正试图使用ARM板上的UART连接从RS485适配器读取寄存器,但没有成功

  • ARM板:CM-T335-TI AM335x Computer-on-Module http://www.computerab.co.il/products/Computer-on-modules/CM-T335/
  • PC:运行Ubuntu的x86计算机
  • 从设备:Elnet Pico(能量功率计)-作为modbus从设备工作,并在请求时使用modbus协议http://Elnet.feniks-pro.com/documents/user_manual/Elnet%20Pico%20-%20user%20manual.pdf向主设备发送能量状态

连接器

  • Rx/Tx电缆
  • Sena RS485适配器:http://www.senanetworks.com/download/datasheet/ds_ltc100.pdf
  • 男性-男性COM适配器:http://i.ebayimg.COM/images/i/300758549547-0-1/s-l1000.jpg
  • 超迷你串行到DB9电缆:https://cdn3.yawarra.com.au/wp-content/uploads/Ultra-mini-Serial-db9-adapter_600x600.jpg

能量功率计<--Rx/Tx电缆-->SENA RS485适配器<-串行阳接/阳接适配器+串行至迷你串行电缆-->ARM板迷你串行端口

查看设置的图像:

  • https://ibin.co/3ccvtvppiuwq.jpg
  • https://ibin.co/3ccvhrr3cqjr.jpg
  • https://ibin.co/3ccw5unqtw8b.jpg
  • https://ibin.co/3ccvuys1tugt.jpg

设备树资源:http://get-album.com/dts/

与PC机连接的从设备

能量功率计<--2线Rx/Tx-->SENA RS485适配器<-->PC

#include <sys/types.h>
#include <string.h>
#include <modbus.h>
#include <stdlib.h>
#include <stdio.h>
#include <errno.h> 

#define MODBUS_DEVICE "/dev/ttyS2"
#define MODBUS_STOP_BIT 1
#define MODBUS_DATA_BIT 8
#define MODBUS_START_BIT 1
#define MODBUS_PARITY 'N'

int main(int argc, char *argv[]) {

    const char *dev_path = MODBUS_DEVICE;
    uint16_t result[2];
    int slave_nr = 31, baud = 9600;
    modbus_t *mb;

    if (argc == 2) {
        dev_path=argv[1];
    } 

    mb = modbus_new_rtu(dev_path, baud, MODBUS_PARITY, MODBUS_DATA_BIT, MODBUS_STOP_BIT);
    if (mb == NULL) {
        printf("error creating libmodbus rtu\n");
        return -1;
    }
    printf("created new rtu...\n");
    modbus_set_debug(mb, 1);
    if (modbus_connect(mb) < 0 ){
        printf("modbus error: %s\n", modbus_strerror(errno));
        modbus_close(mb);
        modbus_free(mb);
        return -1;
    }

    modbus_set_slave(mb, slave_nr);

    printf("ModBus connected !\n");

    if (modbus_read_registers(mb, 0x1, 2, result) < 0) {
        printf("error reading bits: %s\n", modbus_strerror(errno));
        modbus_close(mb);
        modbus_free(mb); 
        return -1;
    }

    printf("successfully red integer: %d:  %X (hex)\n", result[0], result[0]);

    modbus_free(mb);
    return 0;
}
root@cm-debian:~/new# modbus gcc -I /usr/local/include/modbus libmodbus_test.c -o libmodbus_test -lmodbus
root@cm-debian:~/new# ./libmodbus_test /dev/ttyS2
created new rtu...
Opening /dev/ttyS2 at 9600 bauds (N, 8, 1)
ModBus connected !
[1F][03][00][01][00][02][96][75]
Waiting for a confirmation...
<1F><03><04><00><DD><00><DD><54><51>
successfully red integer: 221:  DD (hex)

[ARM板上运行libmodbus_test的输出]

root@cm-debian:~/new# gcc -I /usr/include/modbus/ libmodbus_test.c -o libmodbus_test -lmodbus
root@cm-debian:~/new# ./libmodbus_test /dev/ttyO0
created new rtu...
Opening /dev/ttyO0 at 9600 bauds (N, 8, 1)
ModBus connected !
[1F][03][00][01][00][02][96][75]
Waiting for a confirmation...
ERROR Connection timed out: select

当从ARM板执行libmodbus_test时,select()总是返回0,而在PC上运行相同的程序时,它工作得很好=>从设备返回数据。

使用termios的尝试也失败了,结果类似

#include <sys/select.h>
#include <termios.h>
#include <stdio.h>
#include <fcntl.h>
#include <unistd.h>
#include <sys/time.h>
#include <sys/types.h>
#include <string.h>
#include <stdint.h>
#include <linux/serial.h>
#include <sys/ioctl.h>

static const uint8_t table_crc_hi[] = {
    0x00, 0xC1, 0x81, 0x40, 0x01, 0xC0, 0x80, 0x41, 0x01, 0xC0,
    0x80, 0x41, 0x00, 0xC1, 0x81, 0x40, 0x01, 0xC0, 0x80, 0x41,
    0x00, 0xC1, 0x81, 0x40, 0x00, 0xC1, 0x81, 0x40, 0x01, 0xC0,
    0x80, 0x41, 0x01, 0xC0, 0x80, 0x41, 0x00, 0xC1, 0x81, 0x40,
    0x00, 0xC1, 0x81, 0x40, 0x01, 0xC0, 0x80, 0x41, 0x00, 0xC1,
    0x81, 0x40, 0x01, 0xC0, 0x80, 0x41, 0x01, 0xC0, 0x80, 0x41,
    0x00, 0xC1, 0x81, 0x40, 0x01, 0xC0, 0x80, 0x41, 0x00, 0xC1,
    0x81, 0x40, 0x00, 0xC1, 0x81, 0x40, 0x01, 0xC0, 0x80, 0x41,
    0x00, 0xC1, 0x81, 0x40, 0x01, 0xC0, 0x80, 0x41, 0x01, 0xC0,
    0x80, 0x41, 0x00, 0xC1, 0x81, 0x40, 0x00, 0xC1, 0x81, 0x40,
    0x01, 0xC0, 0x80, 0x41, 0x01, 0xC0, 0x80, 0x41, 0x00, 0xC1,
    0x81, 0x40, 0x01, 0xC0, 0x80, 0x41, 0x00, 0xC1, 0x81, 0x40,
    0x00, 0xC1, 0x81, 0x40, 0x01, 0xC0, 0x80, 0x41, 0x01, 0xC0,
    0x80, 0x41, 0x00, 0xC1, 0x81, 0x40, 0x00, 0xC1, 0x81, 0x40,
    0x01, 0xC0, 0x80, 0x41, 0x00, 0xC1, 0x81, 0x40, 0x01, 0xC0,
    0x80, 0x41, 0x01, 0xC0, 0x80, 0x41, 0x00, 0xC1, 0x81, 0x40,
    0x00, 0xC1, 0x81, 0x40, 0x01, 0xC0, 0x80, 0x41, 0x01, 0xC0,
    0x80, 0x41, 0x00, 0xC1, 0x81, 0x40, 0x01, 0xC0, 0x80, 0x41,
    0x00, 0xC1, 0x81, 0x40, 0x00, 0xC1, 0x81, 0x40, 0x01, 0xC0,
    0x80, 0x41, 0x00, 0xC1, 0x81, 0x40, 0x01, 0xC0, 0x80, 0x41,
    0x01, 0xC0, 0x80, 0x41, 0x00, 0xC1, 0x81, 0x40, 0x01, 0xC0,
    0x80, 0x41, 0x00, 0xC1, 0x81, 0x40, 0x00, 0xC1, 0x81, 0x40,
    0x01, 0xC0, 0x80, 0x41, 0x01, 0xC0, 0x80, 0x41, 0x00, 0xC1,
    0x81, 0x40, 0x00, 0xC1, 0x81, 0x40, 0x01, 0xC0, 0x80, 0x41,
    0x00, 0xC1, 0x81, 0x40, 0x01, 0xC0, 0x80, 0x41, 0x01, 0xC0,
    0x80, 0x41, 0x00, 0xC1, 0x81, 0x40
};


/* Table of CRC values for low-order byte */
static const uint8_t table_crc_lo[] = {
    0x00, 0xC0, 0xC1, 0x01, 0xC3, 0x03, 0x02, 0xC2, 0xC6, 0x06,
    0x07, 0xC7, 0x05, 0xC5, 0xC4, 0x04, 0xCC, 0x0C, 0x0D, 0xCD,
    0x0F, 0xCF, 0xCE, 0x0E, 0x0A, 0xCA, 0xCB, 0x0B, 0xC9, 0x09,
    0x08, 0xC8, 0xD8, 0x18, 0x19, 0xD9, 0x1B, 0xDB, 0xDA, 0x1A,
    0x1E, 0xDE, 0xDF, 0x1F, 0xDD, 0x1D, 0x1C, 0xDC, 0x14, 0xD4,
    0xD5, 0x15, 0xD7, 0x17, 0x16, 0xD6, 0xD2, 0x12, 0x13, 0xD3,
    0x11, 0xD1, 0xD0, 0x10, 0xF0, 0x30, 0x31, 0xF1, 0x33, 0xF3,
    0xF2, 0x32, 0x36, 0xF6, 0xF7, 0x37, 0xF5, 0x35, 0x34, 0xF4,
    0x3C, 0xFC, 0xFD, 0x3D, 0xFF, 0x3F, 0x3E, 0xFE, 0xFA, 0x3A,
    0x3B, 0xFB, 0x39, 0xF9, 0xF8, 0x38, 0x28, 0xE8, 0xE9, 0x29,
    0xEB, 0x2B, 0x2A, 0xEA, 0xEE, 0x2E, 0x2F, 0xEF, 0x2D, 0xED,
    0xEC, 0x2C, 0xE4, 0x24, 0x25, 0xE5, 0x27, 0xE7, 0xE6, 0x26,
    0x22, 0xE2, 0xE3, 0x23, 0xE1, 0x21, 0x20, 0xE0, 0xA0, 0x60,
    0x61, 0xA1, 0x63, 0xA3, 0xA2, 0x62, 0x66, 0xA6, 0xA7, 0x67,
    0xA5, 0x65, 0x64, 0xA4, 0x6C, 0xAC, 0xAD, 0x6D, 0xAF, 0x6F,
    0x6E, 0xAE, 0xAA, 0x6A, 0x6B, 0xAB, 0x69, 0xA9, 0xA8, 0x68,
    0x78, 0xB8, 0xB9, 0x79, 0xBB, 0x7B, 0x7A, 0xBA, 0xBE, 0x7E,
    0x7F, 0xBF, 0x7D, 0xBD, 0xBC, 0x7C, 0xB4, 0x74, 0x75, 0xB5,
    0x77, 0xB7, 0xB6, 0x76, 0x72, 0xB2, 0xB3, 0x73, 0xB1, 0x71,
    0x70, 0xB0, 0x50, 0x90, 0x91, 0x51, 0x93, 0x53, 0x52, 0x92,
    0x96, 0x56, 0x57, 0x97, 0x55, 0x95, 0x94, 0x54, 0x9C, 0x5C,
    0x5D, 0x9D, 0x5F, 0x9F, 0x9E, 0x5E, 0x5A, 0x9A, 0x9B, 0x5B,
    0x99, 0x59, 0x58, 0x98, 0x88, 0x48, 0x49, 0x89, 0x4B, 0x8B,
    0x8A, 0x4A, 0x4E, 0x8E, 0x8F, 0x4F, 0x8D, 0x4D, 0x4C, 0x8C,
    0x44, 0x84, 0x85, 0x45, 0x87, 0x47, 0x46, 0x86, 0x82, 0x42,
    0x43, 0x83, 0x41, 0x81, 0x80, 0x40
};


void calc_crc(uint8_t *buffer, ssize_t length, uint8_t *crc_hi_arg, uint8_t *crc_lo_arg) {

    uint8_t crc_hi = 0xff;
    uint8_t crc_lo = 0xff;
    unsigned int i;

    while (length--) {
        i = crc_hi ^ *buffer++;
        crc_hi = crc_lo ^ table_crc_hi[i];
        crc_lo = table_crc_lo[i];
    }

    *crc_hi_arg = crc_hi;
    *crc_lo_arg = crc_lo;

}

int main(int argc, char **argv){

    char *dev_path = "/dev/ttyS2";
    if (argc == 2) {
        dev_path = argv[1];
    }
    uint8_t write_data[8];
    int fd,write_len,select_ret, bytes_avail, status;
    struct termios config;
    char c;
    uint8_t crc_hi, crc_lo;
    fd_set activefs, tmpfs;;
    struct timeval timeout;

    timeout.tv_sec = 0;
    timeout.tv_usec= 500000;

    fd = open(dev_path, O_RDWR | O_NOCTTY | O_NDELAY | O_EXCL);

    if (fd == -1){
        perror("open");
        return 1;
    } 

    FD_ZERO(&tmpfs);
    FD_SET(fd, &tmpfs);

    printf("opened device\n");
    if (tcgetattr(fd, &config) < 0) { close(fd); return -1 }

    if (cfsetispeed(&config, B9600) < 0 || cfsetospeed(&config, B9600) < 0) {
        printf("cant setting speed!\n");
        close(fd);
        return 1;
    }


    config.c_cflag |= (CREAD | CLOCAL);
    config.c_cflag &=~ CSIZE;
    config.c_cflag &=~ CSTOPB;
    config.c_cflag &=~ PARENB;
    config.c_cflag |= CS8;

    config.c_lflag &= ~(ICANON | ECHO | ECHOE | ISIG);

    config.c_iflag &= ~INPCK;
    config.c_iflag &= ~(IXON | IXOFF| IXANY);

    config.c_oflag &= ~OPOST;


    config.c_cc[VMIN] = 0;
    config.c_cc[VTIME] = 0;

    if (tcsetattr(fd, TCSANOW, &config) < 0) {
        printf("cant apply config!\n");
        close(fd);
        return 1;
    }


    write_data[0] = 0x1f; // slave addr
    write_data[1] = 0x03; // function
    write_data[2] = 0x00; // data address of first coil (8b)
    write_data[3] = 0x01; // data address of first coil (8b)
    write_data[4] = 0x00; // num of coils requested
    write_data[5] = 0x01; // num of coils requested
    calc_crc(write_data, 6, &crc_hi, &crc_lo);
    write_data[6] = crc_hi;
    write_data[7] = crc_lo;

    printf("data: [0x%x][0x%x][0x%x][0x%x][0x%x][0x%x][0x%x][0x%x]", write_data[0], write_data[1], write_data[2], write_data[3], write_data[4], write_data[5], write_data[6], write_data[7]);

    while (1) {

        sleep(1);
        write_len= write(fd, write_data, 8);
        activefs = tmpfs;
        select_ret = select(1, &activefs, NULL, NULL, &timeout);
        if (select_ret < 0) {
            perror("select");
            return 1;
        }

        if (select_ret > 0) {
            printf("select returned %d\n", select_ret);
            if (read(fd, &c, 1) < 0) {
                perror("read");
            } else {
                printf("received: %d\n", c);
            }
        }

    }


}
root@cm-debian:~/new# ./termios /dev/ttyO0
opened device

[PC上Termios.c的输出]

$ gcc -o termios_test termios_test.c
$ ./termios_test /dev/ttyS2
opened device
data: [0x1f][0x3][0x0][0x1][0x0][0x1][0xd6][0x74]select returned 1
received: 31
select returned 1

不要管值,有一个数据交换,这就是我想用板子实现的

板与PC之间的连接是通过超迷你串行到DB9电缆完成的,我可以成功地从板读/写数据。为什么从RS485适配器读取数据从不成功?我应该在哪里寻找才能更接近一个解决方案?

这里有一些关于板/驱动器/等的信息

root@cm-debian:~/modbus# uname -a
Linux cm-debian 4.4.0-cm-t335-5.1 #98 SMP Thu Sep 1 15:12:31 IDT 2016 armv7l GNU/Linux

root@cm-debian:~/new# dmesg | grep -i --color '\(serial\|tty\|uart\)'
[    0.000000] Kernel command line: console=ttyO0,115200n8 root=ubi0:rootfs rw rootfstype=ubifs ubi.mtd=rootfs
[    0.771007] Serial: 8250/16550 driver, 4 ports, IRQ sharing enabled
[    0.780286] omap_uart 44e09000.serial: no wakeirq for uart0
[    0.780329] of_get_named_gpiod_flags: can't parse 'rts-gpio' property of node '/ocp/serial@44e09000[0]'
[    0.780960] 44e09000.serial: ttyO0 at MMIO 0x44e09000 (irq = 155, base_baud = 3000000) is a OMAP UART0
[    1.543031] console [ttyO0] enabled
[    1.550036] omap_uart 48022000.serial: no wakeirq for uart1
[    1.556099] of_get_named_gpiod_flags: can't parse 'rts-gpio' property of node '/ocp/serial@48022000[0]'
[    1.556764] 48022000.serial: ttyO1 at MMIO 0x48022000 (irq = 156, base_baud = 3000000) is a OMAP UART1
[    2.953486] usb usb1: New USB device strings: Mfr=3, Product=2, SerialNumber=1
[    2.973176] usb usb1: SerialNumber: musb-hdrc.0.auto
[    3.572722] usb 1-1: New USB device strings: Mfr=0, Product=0, SerialNumber=0
[    6.689030] systemd[1]: Expecting device dev-ttyO0.device...
[    7.210727] systemd[1]: Starting system-getty.slice.
[    7.235407] systemd[1]: Created slice system-getty.slice.
[    7.241302] systemd[1]: Starting system-serial\x2dgetty.slice.
[    7.265277] systemd[1]: Created slice system-serial\x2dgetty.slice.
[    7.925632] systemd[1]: Starting LSB: controls configuration of serial ports...
[    8.485680] systemd[1]: Started LSB: controls configuration of serial ports.
[   14.840532] pinctrl-single 44e10800.pinmux: pin 44e10978.0 already requested by 48022000.serial; cannot claim for 481cc000.can
[   14.895866] pinctrl-single 44e10800.pinmux: pin 44e10980.0 already requested by 48022000.serial; cannot claim for 481d0000.can


root@cm-debian:~/modbus# setserial -a /dev/ttyO0
/dev/ttyO0, Line 0, UART: undefined, Port: 0x0000, IRQ: 155
        Baud_base: 3000000, close_delay: 50, divisor: 0
        closing_wait: 3000
        Flags: spd_normal

root@cm-debian:~/new# setserial -a /dev/ttyS2
/dev/ttyS2, Line 2, UART: unknown, Port: 0x0000, IRQ: 0
        Baud_base: 0, close_delay: 50, divisor: 0
        closing_wait: 3000
        Flags: spd_normal

root@cm-debian:~/new# setserial -a /dev/ttyS1
/dev/ttyS1, Line 1, UART: unknown, Port: 0x0000, IRQ: 0
        Baud_base: 0, close_delay: 50, divisor: 0
        closing_wait: 3000
        Flags: spd_normal

root@cm-debian:~/new# setserial -a /dev/ttyS0
/dev/ttyS0, Line 0, UART: unknown, Port: 0x0000, IRQ: 0
        Baud_base: 0, close_delay: 50, divisor: 0
        closing_wait: 3000
        Flags: spd_normal


root@cm-debian:~/modbus# lsmod
Module                  Size  Used by
sha256_generic          9731  1
hmac                    2866  1
drbg                   13731  1
ctr                     3673  2
ccm                     7928  2
arc4                    2000  2
wl12xx                 57190  0
wlcore                180594  1 wl12xx
mac80211              605465  2 wl12xx,wlcore
cfg80211              492985  2 mac80211,wlcore
snd_soc_davinci_mcasp    15953  2
snd_soc_tlv320aic23_i2c     2092  1
snd_soc_simple_card     7474  0
snd_soc_tlv320aic23    10191  1 snd_soc_tlv320aic23_i2c
snd_soc_edma            1309  1 snd_soc_davinci_mcasp
snd_soc_core          158330  5 snd_soc_davinci_mcasp,snd_soc_edma,snd_soc_tlv320aic23_i2c,snd_soc_tlv320aic23,snd_soc_simple_card
snd_pcm_dmaengine       5548  1 snd_soc_core
snd_pcm                92743  4 snd_soc_davinci_mcasp,snd_soc_core,snd_soc_tlv320aic23,snd_pcm_dmaengine
c_can_platform          6650  0
c_can                   9638  1 c_can_platform
wlcore_spi              5086  0
can_dev                12315  1 c_can
ti_am335x_adc           5635  0
snd_timer              21413  1 snd_pcm
kfifo_buf               3452  1 ti_am335x_adc
snd                    55936  3 snd_soc_core,snd_timer,snd_pcm
industrialio           40286  2 ti_am335x_adc,kfifo_buf
evdev                  13187  0
omap_wdt                5293  0
soundcore               1339  1 snd


root@cm-debian:~/new# cat /proc/cpuinfo
processor       : 0
model name      : ARMv7 Processor rev 2 (v7l)
BogoMIPS        : 597.60
Features        : half thumb fastmult vfp edsp thumbee neon vfpv3 tls vfpd32
CPU implementer : 0x41
CPU architecture: 7
CPU variant     : 0x3
CPU part        : 0xc08
CPU revision    : 2

Hardware        : Generic AM33XX (Flattened Device Tree)
Revision        : 0000
Serial          : 0000000000000000

root@cm-debian:~/new# cat /proc/consoles
ttyO0                -W- (EC p  )  250:0

root@cm-debian:/etc# cat debian_version
8.2

共有1个答案

勾通
2023-03-14

termios_test.c中发现了两个软件问题。第一个问题与遗漏tcgetattr()有关。第二个是选择()的第一个参数必须是1,而不是fd+1。现在他们修复了,代码仍然不能与塞纳RS485工作。

建议将ARM板连接到PC上,并检查ARM板上的UART是否配置正确。Smokie使用超迷你串行到DB9电缆将ARM连接到PC上,并确认Termios_test.c可以向windows PC发送和接收数据。

就目前而言,我认为问题出在ARM与Sena的物理连接上。用于连接ARM到PC的超迷你串行到DB9电缆是一种可交叉的。它将ARM RX引脚连接到PC TX引脚,反之亦然。塞纳RS485适配器的目的是直接连接到PC没有任何电缆。它有直接连接:PC TX引脚连接到SENA TX引脚和PC RX引脚连接到SENA RX引脚。ARM使用ultra mini串行到DB9电缆和公阳COM适配器连接到SENA。男性-男性COM适配器不改变引脚顺序,所以TX引脚变成了TX引脚。因此,在连接臂TX引脚变得错误,连接到塞纳RX引脚。

ARM side                              SENA side
TXT pin 3                        <--> RXD pin 2
RXD pin 2                        <--> TXT pin 3
GND                              <--> GND
RTS pin 7 (leave unconnected)     +-> RTS pin 7
                                  |
CTS pin 8 (leave unconnected)     +-> CTS pin 8
                                  |
DTR pin 4 (leave unconnected)     +--> DTR pin 4 (to emulate the same behavior as PC does)
DCD pin 1 (leave unconnected)     (leave unconnected) DCD pin 1
DSR pin 6 (leave unconnected)     (leave unconnected) DSR pin 6

可以将RTS和CTS引脚连接到ARM上,以实现硬件流控制,但这并不是必须的。因为SENA RS485 Tx/Rx速度与UART速度相同。无论如何,应该进行以下更改:安装R44和R45(不安装在ARM板上),修改ARM板DTS文件中的RTS/CTS引脚(现在用作I2C1引脚),并在软件中设置UART以使用流量控制。

如果有人在ARM上声明UART,您将在数据流中看到意外的字符(例如,如果ARM使用UART0作为控制台,您将在ARM引导期间看到SENA TX pin闪烁)。或者,如果getty使用UART,您将在数据流中看到“login:”或“login不正确”标记。此外,ARM引导ROM可以打印一些字符串到UART,你不能禁用这种行为。U-boot可能使用UART作为控制台和输出横幅字符串。准备好这样的数据将进入RS485,并以某种方式影响它的工作。

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