diff options
author | Petteri Aimonen <jpa@git.mail.kapsi.fi> | 2013-11-17 19:20:04 +0200 |
---|---|---|
committer | Petteri Aimonen <jpa@git.mail.kapsi.fi> | 2013-12-29 20:26:57 +0200 |
commit | ef31774cd902a6f069b8f2b80b870167328f5acb (patch) | |
tree | 321c008c224a5e197925030e1ddafcc0a88536d6 /examples/using_double_on_avr/README.txt | |
parent | 480b39cc0adc749ad81183fad2bfce6548c56604 (diff) |
Moving files around
Renamed READMEs to README.txt to be more friendly for Windows users.
Diffstat (limited to 'examples/using_double_on_avr/README.txt')
-rw-r--r-- | examples/using_double_on_avr/README.txt | 25 |
1 files changed, 25 insertions, 0 deletions
diff --git a/examples/using_double_on_avr/README.txt b/examples/using_double_on_avr/README.txt new file mode 100644 index 00000000..d9fcdfc6 --- /dev/null +++ b/examples/using_double_on_avr/README.txt @@ -0,0 +1,25 @@ +Nanopb example "using_double_on_avr" +==================================== + +Some processors/compilers, such as AVR-GCC, do not support the double +datatype. Instead, they have sizeof(double) == 4. Because protocol +binary format uses the double encoding directly, this causes trouble +if the protocol in .proto requires double fields. + +This directory contains a solution to this problem. It uses uint64_t +to store the raw wire values, because its size is correct on all +platforms. The file double_conversion.c provides functions that +convert these values to/from floats, without relying on compiler +support. + +To use this method, you need to make some modifications to your code: + +1) Change all 'double' fields into 'fixed64' in the .proto. + +2) Whenever writing to a 'double' field, use float_to_double(). + +3) Whenever reading a 'double' field, use double_to_float(). + +The conversion routines are as accurate as the float datatype can +be. Furthermore, they should handle all special values (NaN, inf, denormalized +numbers) correctly. There are testcases in test_conversions.c. |