Fix broken audio when changing a filter type.

firmware/code/.gitignore

@@ -2,3 +2,4 @@
 inc/
 lib/
 build/
+version.h

firmware/code/CMakeLists.txt

@@ -19,18 +19,48 @@ add_executable(ploopy_headphones
     configuration_manager.c
 )
 
-target_include_directories(ploopy_headphones PRIVATE ${CMAKE_SOURCE_DIR})
+target_include_directories(ploopy_headphones PRIVATE
+    ${CMAKE_SOURCE_DIR}
+    ${CMAKE_BINARY_DIR}/generated
+    )
 
 pico_generate_pio_header(ploopy_headphones ${CMAKE_CURRENT_LIST_DIR}/i2s.pio)
 
+# in case Git is not available, we default to "unknown"
+set(GIT_HASH "unknown")
+
+# find Git and if available set GIT_HASH variable
+find_package(Git QUIET)
+if(GIT_FOUND)
+  execute_process(
+    COMMAND ${GIT_EXECUTABLE} describe --always --dirty
+    OUTPUT_VARIABLE GIT_HASH
+    OUTPUT_STRIP_TRAILING_WHITESPACE
+    ERROR_QUIET
+    )
+endif()
+
+message(STATUS "Git hash is ${GIT_HASH}")
+
+# generate file version.hpp based on version.hpp.in
+configure_file(
+  ${CMAKE_CURRENT_LIST_DIR}/version.h.in
+  ${CMAKE_BINARY_DIR}/generated/version.h
+  @ONLY
+  )
+
+list(APPEND SOURCES "${CMAKE_CURRENT_BINARY_DIR}/version.cc" version.hh)
+
 target_compile_definitions(ploopy_headphones PRIVATE
     # ours are zero based, so say so
     PICO_USBDEV_USE_ZERO_BASED_INTERFACES=1
 
     # need large descriptor
     PICO_USBDEV_MAX_DESCRIPTOR_SIZE=256
-
     PICO_USBDEV_ISOCHRONOUS_BUFFER_STRIDE_TYPE=1
+
+    # make the git hash available to the firmware
+    GIT_HASH="${GIT_HASH}"
 )
 
 pico_enable_stdio_usb(ploopy_headphones 0)

firmware/code/version.h.in

@@ -0,0 +1,5 @@
+#ifndef VERSION_H
+#define VERSION_H
+/** This template is populated by cmake at build time. */
+static const char* FIRMWARE_GIT_HASH = "@GIT_HASH@";
+#endif