Added FS calls for SBC mode

Modified SPI timing and implemented M576 (set SPI comms parameters)
RRF with SBC support reports to SBC when operating in standalone mode
File write buffers are smaller in SBC mode to speed up flush requests

Changes are tested and working with Duet Mini5+, SBC, and LIS3DH
All other build configs compile without warnings but still experimental
TBD:
- Refactor FileWriteBuffer class for read/write instead of write-only
- Use alternative read buffers and get rid of GetFileChunk
- Review fsMutex locks with new SBC calls

1 files changed, 5 insertions, 0 deletions

diff --git a/src/RepRapFirmware.h b/src/RepRapFirmware.h
index 65b2ff8d..edc921e0 100644
--- a/src/RepRapFirmware.h
+++ b/src/RepRapFirmware.h
@@ -514,6 +514,11 @@ constexpr size_t NumCoordinateSystems = 1;
 
 #define DEGREE_SYMBOL	"\xC2\xB0"									// degree-symbol encoding in UTF8
 
+#if HAS_LINUX_INTERFACE
+typedef uint32_t FileHandle;
+const FileHandle noFileHandle = 0;
+#endif
+
 // Type of an offset in a file
 typedef uint32_t FilePosition;
 const FilePosition noFilePosition = 0xFFFFFFFF;