[cmake] build examples w/ a specified driver

cmake/AutoConfig_RF24_DRIVER.cmake

@@ -0,0 +1,56 @@
+set(RF24_LINKED_DRIVER "")
+set(RF24_DRIVER "UNKNOWN" CACHE STRING "override automatic configuration of RF24's utility driver.
+    Specify 1 of the following supported drivers (ie -DRF24_DRIVER=SPIDEV):
+    wiringPi
+    RPi
+    SPIDEV
+    MRAA
+    LittleWire
+    pigpio"
+)
+
+###########################
+# detect pre-existing (locally installed) 3rd party libraries
+###########################
+
+# detect installed libraries despite what RF24_DRIVER is set to
+# this is always done for cross-compiling purposes
+find_library(LibMRAA mraa)
+find_library(LibWiringPi wiringPi)
+find_library(LibLittleWire littlewire-spi)
+find_library(LibPIGPIO pigpio)
+if(EXISTS /dev/spidev0.0)
+    set(SPIDEV_EXISTS TRUE)
+else()
+    set(SPIDEV_EXISTS FALSE)
+endif()
+
+
+if(${RF24_DRIVER} STREQUAL "UNKNOWN") # invokes automatic configuration
+    if("${SOC}" STREQUAL "BCM2708" OR "${SOC}" STREQUAL "BCM2709" OR "${SOC}" STREQUAL "BCM2835")
+        set(RF24_DRIVER RPi CACHE STRING "using folder /utility/RPi" FORCE)
+    elseif(NOT "${LibPIGPIO}" STREQUAL "LibPIGPIO-NOTFOUND")
+        message(STATUS "Found pigpio library: ${LibPIGPIO}")
+        set(RF24_DRIVER pigpio CACHE STRING "using folder /utility/pigpio" FORCE)
+    elseif(NOT "${LibWiringPi}" STREQUAL "LibWiringPi-NOTFOUND")
+        message(STATUS "Found wiringPi library: ${LibWiringPi}")
+        set(RF24_DRIVER wiringPi CACHE STRING "using folder /utility/wiringPi" FORCE)
+    elseif(NOT "${LibLittleWire}" STREQUAL "LibLittleWire-NOTFOUND")
+        message(STATUS "Found LittleWire library: ${LibLittleWire}")
+        set(RF24_DRIVER LittleWire CACHE STRING "using folder /utility/LittleWire" FORCE)
+    elseif(NOT "${LibMRAA}" STREQUAL "LibMRAA-NOTFOUND")
+        message(STATUS "Found MRAA library: ${LibMRAA}")
+        set(RF24_DRIVER MRAA CACHE STRING "using folder /utility/MRAA" FORCE)
+    elseif(SPIDEV_EXISTS) # should be a non-empty string if SPI is enabled
+        message(STATUS "detected that SPIDEV is enabled: ${SPIDEV_EXISTS}")
+        set(RF24_DRIVER SPIDEV CACHE STRING "using folder /utility/SPIDEV" FORCE)
+    endif()
+endif()
+
+# override the auto-detect if RF24_DRIVER is defined in an env var
+if(DEFINED ENV{RF24_DRIVER})
+    message(STATUS "RF24_DRIVER (set from env var) = $ENV{RF24_DRIVER}")
+    set(RF24_DRIVER $ENV{RF24_DRIVER} CACHE STRING "" FORCE)
+endif()
+
+message(STATUS "Using driver: ${RF24_DRIVER}")

examples_RPi/CMakeLists.txt

@@ -13,24 +13,48 @@ add_compile_options(-Ofast -Wall) # passing the compiler a `-pthread` flag doesn
 # detect the CPU make and type
 include(../cmake/detectCPU.cmake) # sets the variable SOC accordingly
 
+# detect if any additional libs need be linked to executable (ei RF24_DRIVER)
+include(../cmake/AutoConfig_RF24_DRIVER.cmake)
+
 find_library(RF24 rf24 REQUIRED)
 message(STATUS "using RF24 library: ${RF24}")
 
 find_library(RF24Network rf24network REQUIRED)
 message(STATUS "using RF24Network library: ${RF24Network}")
 
-find_library(LibPIGPIO pigpio)
-if (NOT "${LibPIGPIO}" STREQUAL "LibPIGPIO-NOTFOUND")
-    message(STATUS "linking to ${LibPIGPIO} for interrupt support")
+set(linked_libs 
+    ${RF24}
+    pthread # Notice we specify pthread as a linked lib here
+    ${RF24Network}
+)
+
+# append additional libs for linking to the executable
+if("${RF24_DRIVER}" STREQUAL "MRAA")
+    if(NOT "${LibMRAA}" STREQUAL "LibMRAA-NOTFOUND")
+        message(STATUS "linking to ${LibMRAA}")
+        list(APPEND linked_libs ${LibMRAA})
+    else()
+        message(FATAL "Lib ${RF24_DRIVER} not found.")
+    endif()
+elseif("${RF24_DRIVER}" STREQUAL "wiringPi")
+    if(NOT "${LibWiringPi}" STREQUAL "LibWiringPi-NOTFOUND")
+        message(STATUS "linking to ${LibWiringPi}")
+        list(APPEND linked_libs ${LibWiringPi})
+    else()
+        message(FATAL "Lib ${RF24_DRIVER} not found.")
+    endif()
+elseif(NOT "${LibPIGPIO}" STREQUAL "LibPIGPIO-NOTFOUND")
+    if(NOT "${RF24_DRIVER}" STREQUAL "pigpio")
+        message(STATUS "linking to ${LibPIGPIO} for interrupt support")
+    else()
+        message(STATUS "linking to ${LibPIGPIO}")
+    endif()
+    list(APPEND linked_libs ${LibPIGPIO})
 endif()
 
 foreach(example ${EXAMPLES_LIST})
     # make a target
     add_executable(${example} ${example}.cpp)
-    # link the RF24 lib to the target. Notice we specify pthread as a linked lib here
-    if ("${LibPIGPIO}" STREQUAL "LibPIGPIO-NOTFOUND")
-        target_link_libraries(${example} PUBLIC ${RF24} pthread ${RF24Network})
-    else()
-        target_link_libraries(${example} PUBLIC ${RF24} pthread ${RF24Network} ${LibPIGPIO})
-    endif()
+    # link the RF24 lib to the target.
+    target_link_libraries(${example} PUBLIC ${linked_libs})
 endforeach()