Hi,

I have come across this modbus library, ‘libmodbus’. I have compiled and installed it on my system. The header file is located in /usr/local/include/modbus. I am using C to develop my code and my header files are located in corecdp-1.1.1/build/tmp/staging/armv5te-corecdp-linux-gunueabi/usr/include. I am confused as how to link the former header file (modbus). In order to bitbake my application successfully do I need to install libmodbus in this location(corecdp-1.1.1/build/tmp/staging/armv5te-corecdp-linux-gunueabi/usr/include)? I would very much appreciate it if someone could answer my question.

Hi Jesse,

thank you very much for your response. I have so far been unsuccessful in my search for a compatible bitbake recipe however I will continue to search further. I would very much appreciate it if you could let me know any recipe that you might have across in the repository that could be used to build libmodbus.

Regards,

JM

Hi Jesse,

thank you very much for the link. When I tried to build libmodbus with the .bb files on the link somehow I have been getting a check sum error. I think I will contact the author of libmodbus on this one. I appreciate your help.

Regards,

JM

Hi Brandon,

thank you very much for your response. I modified the .bb file as per your suggestion however I got another error when I tried to bitbake libmodbus.

Here is the response I got:

jm@jm-desktop:~/Desktop/corecdp-1.1.1$ bitbake libmodbus

NOTE: Handling BitBake files: / (7982/7982) [100 %]

Parsing of 7982 .bb files complete (7672 cached, 310 parsed). 7723 targets, 327 skipped, 0 masked, 0 errors.

NOTE: Resolving any missing task queue dependencies

ERROR: TaskFailed event exception, aborting

ERROR: Build of /home/jm/Desktop/corecdp-1.1.1/user-collection/recipes/libmodbus/libmodbus_3.0.1.bb do_setscene failed

NOTE: Preparing runqueue

NOTE: Executing runqueue

NOTE: Running task 280 of 448 (ID: 1, /home/jm/Desktop/corecdp-1.1.1/user-collection/recipes/libmodbus/libmodbus_3.0.1.bb, do_setscene)

ERROR: Task 1 (/home/jm/Desktop/corecdp-1.1.1/user-collection/recipes/libmodbus/libmodbus_3.0.1.bb, do_setscene) failed with 256

ERROR: ‘/home/jm/Desktop/corecdp-1.1.1/user-collection/recipes/libmodbus/libmodbus_3.0.1.bb’ failed

NOTE: package libmodbus-3.0.1-r15.15: task do_setscene: Started

ERROR: Function staging_helper failed

NOTE: Task failed: (‘function staging_helper failed’, ‘/home/jm/Desktop/corecdp-1.1.1/build/tmp/work/armv5te-corecdp-linux-gnueabi/libmodbus-3.0.1-r15.15/temp/log.staging_helper.13547’)

ERROR: Logfile of failure stored in: /home/jm/Desktop/corecdp-1.1.1/build/tmp/work/armv5te-corecdp-linux-gnueabi/libmodbus-3.0.1-r15.15/temp/log.staging_helper.13547

Log data follows:

| /home/jm/Desktop/corecdp-1.1.1/build/tmp/work/armv5te-corecdp-linux-gnueabi/libmodbus-3.0.1-r15.15/temp/run.staging_helper.13547: line 909: syntax error near unexpected token `else’

| ERROR: Function staging_helper failed

NOTE: package libmodbus-3.0.1-r15.15: task do_setscene: Failed

ERROR: TaskFailed event exception, aborting

ERROR: Build of /home/jm/Desktop/corecdp-1.1.1/user-collection/recipes/libmodbus/libmodbus_3.0.1.bb do_setscene failed

ERROR: Task 1 (/home/jm/Desktop/corecdp-1.1.1/user-collection/recipes/libmodbus/libmodbus_3.0.1.bb, do_setscene) failed with 256

ERROR: ‘/home/jm/Desktop/corecdp-1.1.1/user-collection/recipes/libmodbus/libmodbus_3.0.1.bb’ failed

ERROR: ‘/home/jm/Desktop/corecdp-1.1.1/user-collection/recipes/libmodbus/libmodbus_3.0.1.bb’ failed

jm@jm-desktop:~/Desktop/corecdp-1.1.1$

I modified the filename of the libmodbus_2.0.3.bb to libmodbus_3.0.1 (as 3.0.1 is the latest version of libmodbus) as well as PV = “3.0.1+git${SRCPV}”. I also made sure that I incremented INC_PR each time I bitabked libmodbus along with incrementing PR = “$INC_PR}.x” (where x is the numerical increment). Any suggestions would be very much appreciated. Thank you and have a great day.

Best Regards,

JM

Hi,

I am posting my question again. Please disregard my previous post (question).

I am trying to communicate with a plc which is a modbus slave through a C program. The program just opens and closes the connection as I basically wanted to test this function first before I proceeded any further:

# include “stdio.h”

# include “stdlib.h”

# include “modbus/modbus.h”

#define plc 0x01

int main(void)

{

modbus_param_t mb_param;

modbus_init_rtu(&mb_param,”/dev/ttyS2″,”none”,8,1);

if (modbus_connect(&mb_param) == -1) {

printf(“Not connectedn”);

exit(1);

}

modbus_close(&mb_param);

}

When I compile this program, I am faced with errors:

mymodbuscomm.c: In function ‘main’:

| mymodbuscomm.c:9: error: ‘modbus_param_t’ undeclared (first use in this function)

| mymodbuscomm.c:9: error: (Each undeclared identifier is reported only once

| mymodbuscomm.c:9: error: for each function it appears in.)

| mymodbuscomm.c:9: error: expected ‘;’ before ‘mb_param’

| mymodbuscomm.c:12: error: ‘mb_param’ undeclared (first use in this function)

| ERROR: Function do_compile failed

My bitbake recipe is as follows:

DESCRIPTION = “modbuscomm”

SECTION = “examples”

LICENSE = “GPL”

PR = “r12”

SRC_URI = “file://mymodbuscomm.c

file://modbus.c

file://modbus.h

file://modbus-data.c

file://modbus-rtu.c

file://modbus-rtu.h

file://modbus-tcp.c

file://modbus-tcp.h”

S = “${WORKDIR}”

do_compile() {

${CC} ${CFLAGS} ${LDFLAGS} mymodbuscomm.c -o mymodbuscomm

${CC} ${CFLAGS} ${LDFLAGS} modbus.c -o modbus

${CC} ${CFLAGS} ${LDFLAGS} modbus-data.c -o modbus-data

${CC} ${CFLAGS} ${LDFLAGS} modbus-rtu.c -o modbus-rtu

${CC} ${CFLAGS} ${LDFLAGS} modbus-tcp.c -o modbus-tcp

}

do_install() {

install -d ${D}${bindir}

install -m 0755 mymodbuscomm ${D}${bindir}

install -m 0755 modbus ${D}${bindir}

install -m 0755 modbus-data ${D}${bindir}

install -m 0755 modbus-rtu ${D}${bindir}

install -m 0755 modbus-tcp ${D}${bindir}

}

Any further suggestions on how to go about solving these errors or any suggestions regarding changes to the bitbake recipe would be very much appreciated. Thank you and have a great day.

Best Regards,

JM

Dear Brandon,

thanks for the response. I got it to work.

Best Regards,

JM