ascii support is only available in the custom libmodbusepsi starting with version 3.1.8; remove dependency in default libmodbus

Author: Karl Herbig

CMakeLists.txt

@@ -72,16 +72,11 @@ set(CMAKE_THREAD_PREFER_PTHREAD TRUE)
 set(THREADS_PREFER_PTHREAD_FLAG TRUE)
 find_package(Threads REQUIRED)
 
-set(LIBMODBUS_MIN_VERSION "3.1.6")
+set(LIBMODBUS_MIN_VERSION "3.1.8")
 find_package(PkgConfig REQUIRED)
 
-pkg_check_modules (LIBMODBUS libmodbusepsi>=${LIBMODBUS_MIN_VERSION})
-if (LIBMODBUS_FOUND)
-  set(LIBMODBUS_NAME modbusepsi)
-else()
-  pkg_check_modules (LIBMODBUS REQUIRED libmodbus>=${LIBMODBUS_MIN_VERSION})
-  set(LIBMODBUS_NAME modbus)
-endif()
+pkg_check_modules (LIBMODBUS REQUIRED libmodbusepsi>=${LIBMODBUS_MIN_VERSION})
+set(LIBMODBUS_NAME modbusepsi)
 
 set(LIBMODBUS_PACKAGE lib${LIBMODBUS_NAME}5)
 set(LIBMODBUSDEV_PACKAGE lib${LIBMODBUS_NAME}-dev)