c – ARM：通过UART读取Modbus总线数据失败

机@H_618_3@

> ARM板：CM-T335 – TI AM335x电脑模块http://www.compulab.co.il/products/computer-on-modules/cm-t335/
> PC：运行Ubuntu的x86机器
>从设备：Elnet Pico(能量功率计) – 作为一个模块从站,当使用modbus协议要求时,向主站发送能量状态http://elnet.feniks-pro.com/documents/User_manual/Elnet%20Pico%20-%20User%20Manual.pdf@H_618_3@

连接器@H_618_3@

> RX / TX电缆
> SENA RS485适配器：http://www.senanetworks.com/download/datasheet/ds_ltc100.pdf
>男 – 公COM适配器：http://i.ebayimg.com/images/i/300758549547-0-1/s-l1000.jpg
>超小型串口到DB9电缆：https://cdn3.yawarra.com.au/wp-content/uploads/Ultra-mini-serial-DB9-adapter_600x600.jpg@H_618_3@

从设备连接到ARM板@H_618_3@

能量功率计< - rx / tx电缆 - > SENA RS485适配器< - 串行公/公适配器串行到迷你串行电缆 - > ARM板迷你串口@H_618_3@

查看设置图像：@H_618_3@

> https://ibin.co/3CCvTVPPIUWQ.jpg
> https://ibin.co/3CCvhrr3CQjr.jpg
> https://ibin.co/3CCw5uNqTW8B.jpg
> https://ibin.co/3CCvuys1tUgt.jpg@H_618_3@

使用的设备树：am335x-sbc-t335.dts@H_618_3@

设备树资源：http://get-album.com/dts/@H_618_3@

从设备连接到PC@H_618_3@

能量功率计< - 2线rx / tx - > SENA RS485适配器个人计算机@H_618_3@

注意：板上的迷你串口与串口控制台通讯使用的端口相同(波特率为115200),而且无任何问题@H_618_3@

以下是使用libmodbus库从连接的从设备读取第一个寄存器的c代码@H_618_3@

libmodbus_test.c – 从设备读取和打印第一个传送器：@H_618_3@

#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;
}

[从PC上运行libmodbus_test输出]@H_618_3@

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)

[从ARM板上运行libmodbus_test输出]@H_618_3@

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,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()始终返回0
在PC上运行相同的程序时,它工作正常=>从设备返回数据.@H_618_3@

使用termios的尝试也失败了类似的结果@H_618_3@

termios_test.c@H_618_3@

#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[] = {
    0x00,0xC1,0x81,0x40,0x01,0xC0,0x80,0x41,0x00,0x40
};


/* Table of CRC values for low-order byte */
static const uint8_t table_crc_lo[] = {
    0x00,0xC3,0x03,0x02,0xC2,0xC6,0x06,0x07,0xC7,0x05,0xC5,0xC4,0x04,0xCC,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,0x44,0x84,0x85,0x45,0x87,0x47,0x46,0x86,0x82,0x42,0x43,0x83,0x40
};


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,&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);
            }
        }

    }


}

[从ARM板上的termios.c输出]@H_618_3@

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

…选择继续返回0@H_618_3@

[从PC上的termios.c输出]@H_618_3@

$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

没关系的价值观,有一个数据交换,这就是我想用板子实现的@H_618_3@

我尝试通过pcntl传递RS485属性,但是发生了相同的结果
termios_rs485_test.c：http://pastebin.com/RWtHtjLF@H_618_3@

板和PC之间的连接通过超小型串行到DB9电缆完成,我可以从板上成功读取/写入数据.如何从RS485适配器读取数据从未成功？我应该在哪里寻找更贴近的解决方案？@H_618_3@

以下是有关板/驱动程序等的一些信息@H_618_3@

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,IRQ: 0
        Baud_base: 0,divisor: 0
        closing_wait: 3000
        Flags: spd_normal

root@cm-debian:~/new# setserial -a /dev/ttyS1
/dev/ttyS1,Line 1,divisor: 0
        closing_wait: 3000
        Flags: spd_normal

root@cm-debian:~/new# setserial -a /dev/ttyS0
/dev/ttyS0,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_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

任何帮助都非常感激
谢谢@H_618_3@

updatE@H_618_3@

虽然超小型串行到DB9电缆连接到电路板,我运行termios_test.c,在运行时,我在电缆的中间插脚(TX)插入了一块金属片,我可以看到屏幕上显示的垃圾数据有时！).我将公头适配器插入电缆,再次触摸中间的针脚,我可以再次看到垃圾数据.@H_618_3@

我所做的另一件事是将从设备连接到SENA RS485适配器,并在接触金属时使用插针上的金属片,适配器的中间插针,使TX LED导通.没有引脚会打开RX引线.将RS485适配器连接到PC的COM端口时,将数据发送到该端口将使RX LED闪烁.我开始怀疑该主板没有正确地写入RS485适配器,或者该引脚没有正确映射.我应该从哪里走？这可能是真的软件问题吗？@H_618_3@