Need Some sort of Jumpstart

[ntd]

Hi @knebb
I developed a fistful of programs in plain C on Neuron. I just linked against libmodbus and called the loopback ModBUS server at 127.0.0.1, port 502 (hence no need to enable the EVOK service).
If you are not familiar I can send you some code to help you getting started.

[martin_triska]

Hello @knebb, as @ntd wrote there is no need to use the Evok (which is, basically a bridge between Modbus server and several web-service interfaces). The simplest option for direct access from a C/C++ application should be the sysfs interface. Of course, a Modbus client connected to the internally running Modbus server can be used also.

[knebb]

@martin_triska @ntd
Great thanks for the hints. Using libmodbus seems to be the way I will go. Seems to be easy enough to use and is available in C. I already found the Neuron Docs regarding the coils and registers.

If you could send me your example code sniplets? How to set the relays, read DI or set DO?

Thanks a lot in advance! first step is done.

/KNEBB

[knebb]

@martin_triska

I checked for the sysfs, too.

I did not see any references to the relays? How can I set relays (Neuron M103 has some) through sysfs?

Thanks again!

/KNEBB

[ntd]

@knebb The relevant function is fieldbus_thread, that basically runs a polling loop every 20 ms. If you do not need threads, you can consider that function as main() and drop all the locking stuff (i.e. a good 50% of code in iteration).

#include "lappaseven.h"
#include "fieldbus.h"
#include <errno.h>
#include <string.h>

#define MODBUS_ID       0

#define AI1_ADDRESS     3
#define DI1_ADDRESS     0
#define DI2_ADDRESS     100
#define DI3_ADDRESS     200
#define DO1_ADDRESS     1
#define DO2_ADDRESS     101
#define DO3_ADDRESS     201
#define AO1_ADDRESS     2
#define VREFINT_ADDRESS 5
#define VREF_ADDRESS    1009


static IO image = { 0 };


void
fieldbus_free(modbus_t *modbus)
{
    if (modbus != NULL) {
        modbus_close(modbus);
        modbus_free(modbus);
    }
}

modbus_t *
fieldbus_new(void)
{
    modbus_t *modbus;
    gchar *host;
    int port;

    host   = g_settings_get_string(gs.settings, "modbus-host");
    port   = g_settings_get_uint(gs.settings, "modbus-porta");
    modbus = modbus_new_tcp(host, port);

    if (modbus == NULL ||
        modbus_connect(modbus) == -1 ||
        modbus_set_slave(modbus, MODBUS_ID) == -1)
    {
        g_warning("Unable to initialize communication on %s:%d: %s",
                  host, port, modbus_strerror(errno));
        fieldbus_free(modbus);
        modbus = NULL;
    }

    g_free(host);
    return modbus;
}

gboolean
fieldbus_get_ai(modbus_t *modbus)
{
    uint16_t vrefint, vref, ai;

    if (modbus_read_registers(modbus, VREFINT_ADDRESS, 1, &vrefint) == -1 ||
        modbus_read_registers(modbus, VREF_ADDRESS, 1, &vref) == -1 ||
        modbus_read_registers(modbus, AI1_ADDRESS, 1, &ai) == -1)
    {
        g_warning("fieldbus_get_ai error: %s", modbus_strerror(errno));
        return FALSE;
    }

    /* Linearization to volts as described by Neuron manual, page 14.
     * AI1vdev and AI1voffset are set to supposedly 0. */
    image.AI1 = 3.3 * vref / vrefint * 3 * ai / 4096;
    return TRUE;
}

gboolean
fieldbus_get_di(modbus_t *modbus)
{
    uint16_t word1, word2, word3;
    int n;

    if (modbus_read_registers(modbus, DI1_ADDRESS, 1, &word1) == -1 ||
        modbus_read_registers(modbus, DI2_ADDRESS, 1, &word2) == -1 ||
        modbus_read_registers(modbus, DI3_ADDRESS, 1, &word3) == -1)
    {
        g_warning("fieldbus_get_di error: %s", modbus_strerror(errno));
        return FALSE;
    }

    for (n = 0; n < G_N_ELEMENTS(image.DI1); ++n) {
        image.DI1[n] = (word1 & (1 << n)) > 0;
    }
    for (n = 0; n < G_N_ELEMENTS(image.DI2); ++n) {
        image.DI2[n] = (word2 & (1 << n)) > 0;
    }
    for (n = 0; n < G_N_ELEMENTS(image.DI3); ++n) {
        image.DI3[n] = (word3 & (1 << n)) > 0;
    }

    return TRUE;
}

gboolean
fieldbus_set_do(modbus_t *modbus)
{
    uint16_t word1, word2, word3;
    int n;

    word1 = 0;
    word2 = 0;
    word3 = 0;

    for (n = 0; n < G_N_ELEMENTS(image.DO1); ++n) {
        word1 |= image.DO1[n] << n;
    }
    for (n = 0; n < G_N_ELEMENTS(image.DO2); ++n) {
        word2 |= image.DO2[n] << n;
    }
    for (n = 0; n < G_N_ELEMENTS(image.DO3); ++n) {
        word3 |= image.DO3[n] << n;
    }

    if (modbus_write_register(modbus, DO1_ADDRESS, word1) == -1 ||
        modbus_write_register(modbus, DO2_ADDRESS, word2) == -1 ||
        modbus_write_register(modbus, DO3_ADDRESS, word3) == -1)
    {
        g_warning("fieldbus_set_do error: %s", modbus_strerror(errno));
        return FALSE;
    }

    return TRUE;
}

gboolean
fieldbus_set_ao(modbus_t *modbus)
{
    /* Analog output must be between 0 .. 5 V, hence the division */
    if (modbus_write_register(modbus, AO1_ADDRESS, image.AO1 / 2) == -1) {
        g_warning("fieldbus_set_ao error: %s", modbus_strerror(errno));
        return FALSE;
    }

    return TRUE;
}

#if THREADING
static gboolean
iteration(modbus_t *modbus)
{
    static gboolean workaround = FALSE;
    gboolean AI, DI, AO, DO, quit;

    AI = fieldbus_get_ai(modbus);
    DI = fieldbus_get_di(modbus);

    g_mutex_lock(&gs.fieldbus_lock);
    AO = gs.hal.AO1 != gs.share.AO1;
    DO = memcmp(gs.hal.DO1, gs.share.DO1, sizeof(gs.hal.DO1)) != 0 ||
         memcmp(gs.hal.DO2, gs.share.DO2, sizeof(gs.hal.DO2)) != 0 ||
         memcmp(gs.hal.DO3, gs.share.DO3, sizeof(gs.hal.DO3)) != 0;
    if (DI) {
        memcpy(gs.share.DI1, image.DI1, sizeof(image.DI1));
        memcpy(gs.share.DI2, image.DI2, sizeof(image.DI2));
        memcpy(gs.share.DI3, image.DI3, sizeof(image.DI3));
    }
    if (AI) {
        gs.share.AI1 = image.AI1;
    }
    if (DO) {
        memcpy(image.DO1, gs.share.DO1, sizeof(image.DO1));
        memcpy(image.DO2, gs.share.DO2, sizeof(image.DO2));
        memcpy(image.DO3, gs.share.DO3, sizeof(image.DO3));
    }
    if (AO) {
        image.AO1 = gs.share.AO1;
    }
    quit = gs.quit;
    g_mutex_unlock(&gs.fieldbus_lock);

    if (DI) {
        memcpy(gs.hal.DI1, image.DI1, sizeof(image.DI1));
        memcpy(gs.hal.DI2, image.DI2, sizeof(image.DI2));
        memcpy(gs.hal.DI3, image.DI3, sizeof(image.DI3));
    }
    if (DO && fieldbus_set_do(modbus)) {
        memcpy(gs.hal.DO1, image.DO1, sizeof(image.DO1));
        memcpy(gs.hal.DO2, image.DO2, sizeof(image.DO2));
        memcpy(gs.hal.DO3, image.DO3, sizeof(image.DO3));
    }

    /* XXX Workaround for a unknown fieldbus error that seems to reset the
     *     analog output: if this happens, force a AO1 refresh cycle */
    if (! DI || ! AI) {
        workaround = TRUE;
    }
    AO = AO || workaround;

    if (AO && fieldbus_set_ao(modbus)) {
        g_debug("AO1 set to %d", image.AO1);
        gs.hal.AO1 = image.AO1;
        workaround = FALSE;
    }

    return ! quit;
}

gpointer
fieldbus_thread(gpointer user_data)
{
    modbus_t *modbus;
    gint64 period, scan, now, span, limit;

    if (gs.dry_run) {
        return NULL;
    }

    modbus = fieldbus_new();
    if (modbus == NULL) {
        return NULL;
    }

    period = g_settings_get_uint(gs.settings, "periodo");
    if (period == 0) {
        g_warning("Period set to 0: fallback to 20000");
        period = 20000;
    }

    scan  = g_get_monotonic_time();
    limit = period;

    do {
        g_main_context_invoke_full(NULL, G_PRIORITY_HIGH,
                                   cycle_iteration, NULL, NULL);
        now  = g_get_monotonic_time();
        span = now - scan;
        if (span > limit) {
            limit = span;
            g_warning("Period exceeded: %.3f ms > %.3f ms" ,
                      limit / 1000., period / 1000.);
        }
        scan += period;
        if (now < scan) {
            g_usleep(scan - now);
        }
    } while (iteration(modbus));

    fieldbus_free(modbus);
    return NULL;
}
#endif

The IO struct is just an image of the I/O status:

typedef struct {
    uint8_t         DI1[4];
    uint8_t         DI2[16];
    uint8_t         DI3[16];
    uint8_t         DO1[4];
    uint8_t         DO2[14];
    uint8_t         DO3[14];
    double          AI1;
    uint16_t        AO1;
} IO;

[knebb]

@ntd Thanks a lot! I think I got it so far. The adresses of the devices you got from Neuron documentation I assume?

Only one question left so far. If I want to write the current state of the relay I would use (according to doc):

//int modbus_write_bit(modbus_t *ctx, int addr, int status);
errlvl=modbus_write_bit(modbus_handle, 100, status);

I am unsure about the "status". This means I will enable or disable the bit and therefore switching the relay, right?

Ok, how about reading the DI 2.1?
Would I use the following?

//int modbus_read_bits(modbus_t *ctx, int addr, int nb, uint8_t *dest);
errlvl=modbus_read_bits(modbus_handle, 108, nb, *dest);

Here I have no clue for what I would need the nb... does it mean it will read nb bits? To be stored in nb*dest? I would always use the value 1, wouldn't I? If using 2 it would return the value of the second DI 2.2 in the second bit, correct?

Thanks a lot in advance!

/KNEBB

[knebb]

Hi,

for reference purposes even though some questions are still unanswered.
I was able to set my relays as expected with the following code:

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

void main()
{

modbus_t *modbusglob;
int errlvl;

void fieldbus_free(modbus_t *modbus)
{
        if (modbus != NULL) {
        modbus_close(modbus);
        modbus_free(modbus);
    }
  return;
}

modbus_t *fieldbus_new(void)
{
    int err;
    modbus_t *modbus;
    char host[15];
    int port;

// Need to use IP as it does not resolve DNS Names to IPs
    strcpy(host,"127.0.0.1");
    port   = 502;
    modbus = modbus_new_tcp(host, port);

    if (modbus == NULL )
    {
         printf("modbus is NULL\n");
        fieldbus_free(modbus);
        exit (55);
    }

     err = modbus_connect(modbus);
     if (err  == -1)
     {
        printf("modbus_connect, %s",modbus_strerror(errno));
        fieldbus_free(modbus);
        exit (55);
     };
 
     err=modbus_set_slave(modbus, 0);
     if(  err == -1)
    {
        printf("modbus_set_slave, %s",modbus_strerror(errno));
        fieldbus_free(modbus);
        modbus = NULL;
        exit (55);
    }

    return modbus;
}

modbusglob=fieldbus_new();
printf("ON\n");
// Using fixed address of 100 here for first relay (M103), relay 2.2 ist 101 and so on.
// Using TRUE as synonym for HIGH or ON
errlvl=modbus_write_bit(modbusglob, 100, TRUE);
// Just for demo purposes- keep the relay on for 10 seconds
sleep(10);
printf("OFF\n");
errlvl=modbus_write_bit(modbusglob, 100, FALSE);
fieldbus_free(modbusglob);
}

[ntd]

@knebb said in Need Some sort of Jumpstart:

I am unsure about the "status".

According to the documentation, status is the new value of the output and can be TRUE (to enable it) or FALSE (to disable it).

Here I have no clue for what I would need the nb... does it mean it will read nb bits? To be stored in nb*dest? I would always use the value 1, wouldn't I? If using 2 it would return the value of the second DI 2.2 in the second bit, correct?

Yes to all. This mimics the behavior of the underlying protocol: ModBUS has a Read coils function but does not have Read single coil. You can easily provide your own macro for that, if you really want:

#define read_bit(bus,addr,dst) modbus_read_bits((bus),(addr),1,(dst))

[knebb]

@ntd

Sorry to bother you. I think I got it finally!
Using modbus_read_bits will read nb bits and write (according to the state) 0 or 1 into dst[0]...dst[nb].
I had thought when reading 4 bits it will write the first state into the first bit of dst, second into the second and so on.

But no, it writes the state as 0 or 1 into each of the uint8_t .

I was successfull in reading RO2.8 and DI2.1 together with

int nb,i;
uint8_t dst[2];
nb=2;
modbus_read_bits(modbus,107,nb,dst);
for (i=0;i<nb;i++)
{
  if (dst[i] != 0) 
  {
    printf("Bit %d is %u\n",i,dst[i]);
  } else {
    printf("Bit %d is %u\n",i,dst[i])
  }
}

And in case RO2.8 is on an DI2.1 is off I will get:
Bit 0 is 1
Bit 1 is 0

Similar this would apply to modbus_read_register();

Holy sh**, I think I really got it now!

Thanks for your patience!

/KNEBB

[ntd]

@knebb said in Need Some sort of Jumpstart:

it writes the state as 0 or 1 into each of the uint8_t .

Or, using semantic constants, as FALSE and TRUE.

Directly using bits would be really slow and error prone (and a nightmare for language bindings).