@knebb
Answering myself as I figured it out by try&error. Use address 2. Use values from 0 to 4096 (as documented).
However, I measured the AO port and never came above 8V (with 4096) with default settings (did not change any of Vref, Vrefint, Voffs, Vdev). Is this measurement issue or something wrong with my code?
/KNEBB
Hi all,
I am on the way in using the C library modbus to read/write to my Neuron M103.
I have a question regarding the documentation:
Here it writes about the calculation of the value to be set for the desired voltage.
Now I checked the Register Docs and found two addresses:
2 Analog Output (raw value) as Obsolete
3000 Analog Output value as Basic
So would I write to address 2 using the calculated value?
Or woud I use the desired voltage (0-10) to write to address 3000?
Or calculate and write to 3000?
Thanks!
/KNEBB
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
Perfect!
Got it finally. I mixed up modbus_read_bits and modbus_read_register. Now working like a charm!
Thanks a lot!
/KNEBB
Thanks for the explanation; I figured it already out Raspbian is littleEndian.
Just to make sure:
To read i.e. the counter for digital input 2.1 (address 103-104 with DWORD, 32bit in total) I would use:
uint8_t counter[4];
modbus_read_bits(bus, 103, 4, counter);
Or this one?
uint8_t counter1[2],counter2[2];
modbus_read_bits(bus, 103, 2, counter1);
modbus_read_bits(bus, 104, 2, counter2);
Would both work?
Sorry for my dumb question, I am really new to modbus...
/KNEBB
@ntd :Thanks a lot four your input, I really appreciate it.
I am just wondering as there seems to be no difference between uint8_t, uint16_t and uint32_t.
See my question here.
When using uint8_t the result is exactly the same. All seem to be 32bit long...
So how does modbus deal with this? It writes only the least significant 8 bits? Others are set to zero?
/KNEBB
Hi,
as I am currently coding my application and I am unsure about electronics. Would the following work for testing purposes? To see the DI changes when DO is set ON? Or is this a really bad idea?
Thanks a lot!
/KNEBB
Hi all,
ok, I manged to use the relays through modbus with libmodbus with my C-code. Now I am trying to use the DI/DO/AO/AI interfaces.
I see the Neuron Registers Map but I am only able to understand it partially...
I am aware the function modbus_read_bits() can be usedd to read the DIs. So I open a modbus_tcp connection with the address of DI2.1 for example:
modbus_read_bits(modbus_handle, 108, nb, *dest);
*dest is supposed to be uint16_t.
I was able to read the above- finally I have some data in *dest. But how do I have to read the data there? I expected something like "bit 1 tells if the DI is currently ON or OFF and bit2 is the counter while writing bit3 will reset the counter" or stuff like this.
So I am a little bit lost here to interpret the values I got.
Nearly the same is for writing. What values should I put into uint16_t to enable the DI?
And how can I configure the AO?
Thanks a lot for hints!
/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 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