diff options
Diffstat (limited to 'docs')
| -rw-r--r-- | docs/reference.rst | 17 |
1 files changed, 12 insertions, 5 deletions
diff --git a/docs/reference.rst b/docs/reference.rst index aefc25f7..3331c6d3 100644 --- a/docs/reference.rst +++ b/docs/reference.rst @@ -10,14 +10,21 @@ Compilation options =================== The following options can be specified using -D switch given to the C compiler: -============================ ============================================================================================== +============================ ================================================================================================ __BIG_ENDIAN__ Set this if your platform stores integers and floats in big-endian format. Mixed-endian systems (different layout for ints and floats) are currently not supported. NANOPB_INTERNALS Set this to expose the field encoder functions that are hidden since nanopb-0.1.3. -PB_MAX_REQUIRED_FIELDS Maximum number of required fields to check for presence. Default value is 64. -PB_MANY_FIELDS Add support for tag numbers > 255 and fields larger than 255 bytes or 255 array entries. +PB_MAX_REQUIRED_FIELDS Maximum number of required fields to check for presence. Default value is 64. Increases stack + usage 1 byte per every 8 fields. Compiler warning will tell if you need this. +PB_FIELD_16BIT Add support for tag numbers > 255 and fields larger than 255 bytes or 255 array entries. + Increases code size 3 bytes per each field. Compiler error will tell if you need this. +PB_FIELD_32BIT Add support for tag numbers > 65535 and fields larger than 65535 bytes or 65535 array entries. Increases code size 9 bytes per each field. Compiler error will tell if you need this. -============================ ============================================================================================== +============================ ================================================================================================ + +The PB_MAX_REQUIRED_FIELDS, PB_FIELD_16BIT and PB_FIELD_32BIT settings allow raising some datatype limits to suit larger messages. +Their need is recognized automatically by C-preprocessor #if-directives in the generated .pb.h files. The default setting is to use +the smallest datatypes (least resources used). pb.h ==== @@ -79,7 +86,7 @@ Describes a single structure field with memory position in relation to others. T :array_size: Maximum number of entries in an array, if it is an array type. :ptr: Pointer to default value for optional fields, or to submessage description for PB_LTYPE_SUBMESSAGE. -The *uint8_t* datatypes limit the maximum size of a single item to 255 bytes and arrays to 255 items. Compiler will give error if the values are too large. The types can be changed to larger ones by defining *PB_MANY_FIELDS*. +The *uint8_t* datatypes limit the maximum size of a single item to 255 bytes and arrays to 255 items. Compiler will give error if the values are too large. The types can be changed to larger ones by defining *PB_FIELD_16BIT*. pb_bytes_array_t ---------------- |