fix most warnings with rp2040 -wconversion

examples/device/usbtmc/CMakeLists.txt

@@ -24,6 +24,9 @@ target_include_directories(${PROJECT} PUBLIC
         ${CMAKE_CURRENT_SOURCE_DIR}/src
         )
 
+# Example common such as compiler warnings
+include(${CMAKE_CURRENT_SOURCE_DIR}/../../example.cmake)
+
 # Configure compilation flags and libraries for the example... see the corresponding function
 # in hw/bsp/FAMILY/family.cmake for details.
 family_configure_device_example(${PROJECT})

examples/device/usbtmc/src/usb_descriptors.c

@@ -175,7 +175,7 @@ uint16_t const* tud_descriptor_string_cb(uint8_t index, uint16_t langid)
     const char* str = string_desc_arr[index];
 
     // Cap at max char
-    chr_count = strlen(str);
+    chr_count = (uint8_t) strlen(str);
     if ( chr_count > 31 ) {
       chr_count = 31;
     }