Raspberry Pi Zero W running Blynk local server and Blynk client to forward data from NRF24L01+ to the local server

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1

My Project:
First of all a short summary of what a plan to do with Blynk:
I want to build many small Low Power Sensor Nodes and place them in ever room of my flat. To be as energy efficient as possible for long runtime a choose an Arduino Pro mini with an NRF24l01+ for this task. Theses Sensor nodes run my very own code. No blynk code running on them.
I want to collect the data from the sensor nodes on a raspberry pi zero w running a local blynk server. I already made it work with an Arduino with an NRF24 connected via USB using the blynk-ser.sh script as well as connecting the Arduino via UART to the raspberry again using blynk-ser.sh script.
But i would like to futher reduce the hardware and the power consumption by removing the arduino and connect the NRF24l01+ directly to the raspberry pi zero w.

What works so far:
By now I am able to run an test programm written in c++ to receive data with the NRF24 (not including any blynk related code or libraries).
I am also able to run the blynk programm (main.cpp) included in the blynk-library for linux to connect the blynk client to the local server.

My Problem:
I am unable to compile the programm (main.cpp) as soon as I try to add Code to create an object of the class RF24. The added lines to the main.cpp and the error of the compiler looks as follows:

#include “/home/pi/RF24/RPi/RF24/RF24.h”

// Setup for GPIO 22 CE and CE0 CSN with SPI Speed @ 8Mhz
RF24 radio(RPI_V2_GPIO_P1_15, RPI_V2_GPIO_P1_24, BCM2835_SPI_SPEED_8MHZ);

main.o: In function _GLOBAL__sub_I_Blynk': main.cpp:(.text.startup+0x994): undefined reference to RF24::RF24(unsigned char, unsigned char, unsigned int)’
collect2: error: ld returned 1 exit status

comments:
I know about node.js and I tried to make the NRF24 run with the node-nrf library but I was unable to. Since I nerver used javascript I turned back to C++ where I am more experienced.
I am quite new to linux and I never dealt with makefile. (It seem to me that my problem is related to the setup of the makefile)
Can anyone help me with my problem, please?

1 Like
2

you’ll have to firure it out… you need to “link” the main application with nrf24 library.

3

thanks for your quick reply!
If possible, can you or someone else explain in more detail where to start searching for the problem.
Is my guess with the makefile right?
I was expecting that including the header file (RF24.h) like shown in the first post would do the job of linking.

4

I managed to merge the makefiles, The program is compiling and running!

My modified makefile looks like this:

# 
# To build on RaspberryPi:
# 1. Install WiringPi: http://wiringpi.com/download-and-install/
# 2. Run:
#    make target=raspberry
#    sudo blynk --token=YourAuthToken
#

CC ?= gcc
CXX ?= g++
CXXFLAGS += -I ../src/ -I ./ -DLINUX -I../ -lrf24-bcm
LDFLAGS += -lrt -lpthread

ifeq ($(build),debug)
	CXXFLAGS += -c -g2 -O0 \
		-Wall -Weffc++ \
		-Wextra -Wcast-align \
		-Wchar-subscripts  -Wcomment -Wconversion \
		-Wdisabled-optimization \
		-Wfloat-equal  -Wformat  -Wformat=2 \
		-Wformat-nonliteral -Wformat-security  \
		-Wformat-y2k \
		-Wimplicit  -Wimport  -Winit-self  -Winline \
		-Winvalid-pch   \
		-Wunsafe-loop-optimizations  -Wlong-long -Wmissing-braces \
		-Wmissing-field-initializers -Wmissing-format-attribute   \
		-Wmissing-include-dirs -Wmissing-noreturn \
		-Wpacked  -Wparentheses  -Wpointer-arith \
		-Wredundant-decls -Wreturn-type \
		-Wsequence-point  -Wshadow -Wsign-compare  -Wstack-protector \
		-Wstrict-aliasing -Wstrict-aliasing=2 -Wswitch  -Wswitch-default \
		-Wswitch-enum -Wtrigraphs  -Wuninitialized \
		-Wunknown-pragmas  -Wunreachable-code -Wunused \
		-Wunused-function  -Wunused-label  \
		-Wunused-value  -Wunused-variable \
		-Wvolatile-register-var  -Wwrite-strings
	
	# Disable some warnings
	CXXFLAGS += -Wno-variadic-macros -Wno-unused-parameter -Wno-vla
	
	# Uncomment this to get pedantic warnings:
	#CXXFLAGS += -pedantic -Wvariadic-macros -Wunused-parameter -Waggregate-return -Wcast-qual -Wpadded
else
	CXXFLAGS += -c -O3 -w
	LDFLAGS += -s
endif

ifeq ($(target),raspberry)
	CXXFLAGS += -DRASPBERRY
	LDFLAGS += -lwiringPi
endif

SOURCES= main.cpp \
	BlynkDebug.cpp \
	../src/utility/BlynkHandlers.cpp \
	../src/utility/BlynkTimer.cpp \
	/home/pi/RF24/RPi/RF24/RF24.cpp

SOURCES2=/home/pi/RF24/RPi/RF24/bcm2835.c


OBJECTS=$(SOURCES:.cpp=.o)
OBJECTS+=$(SOURCES2:.c=.o)

EXECUTABLE=	blynk 

all: $(SOURCES) $(SOURCES2) $(EXECUTABLE)

clean:
	-rm $(OBJECTS) $(EXECUTABLE)

$(EXECUTABLE): $(OBJECTS) 
	$(CXX) $(OBJECTS) $(LDFLAGS) -o $@

.cpp.o:
	$(CXX) $(CXXFLAGS) $< -o $@

The lines I edited are:

CXXFLAGS += -I …/src/ -I ./ -DLINUX -I…/ -lrf24-bcm

/home/pi/RF24/RPi/RF24/RF24.cpp

SOURCES2=/home/pi/RF24/RPi/RF24/bcm2835.c

OBJECTS+=$(SOURCES2:.c=.o)

all: $(SOURCES) $(SOURCES2) $(EXECUTABLE)

2 Likes
5

If you would like to save your program in a folder diffrent to the “/home/pi/blynk-library/linux” folder you have to change the following line of the makefile to:

CXXFLAGS += -I /home/pi/blynk-liibrary/src/ -I ./ -DLINUX -I…/ -lrf24-bcm

SOURCES= main.cpp \
/home/pi/blynk-library/linux/BlynkDebug.cpp \
/home/pi/blynk-library/src/utility/BlynkHandlers.cpp \
/home/pi/blynk-library/src/utility/BlynkTimer.cpp \

you also have to change the path of the included libraries in the main.cpp:

#include </home/pi/blynk-library/linux/BlynkApiWiring.h>
#include </home/pi/blynk-library/linux/BlynkSocket.h>
#include </home/pi/blynk-library/linux/BlynkOptionsParser.h>

If you don’t want to always enter the auth token and the server address when executing your programm you can modify the main function of the main.cpp like this:

int main(int argc, char* argv[])
{
    const char *auth = {"your auth token"}; 
    const char *serv = {"127.0.0.1"};
    uint16_t port    = 8442;

    Blynk.begin(auth, serv, port);

    setup();
    while(true) {
        loop();
    }

    return 0;
}
1 Like