Fix write buffer issues

[madhogs]

3 changes:

1. Flush the write buffer first if it is full rather than overwrite data
2. Fix bug in write loop causing it to exit early
3. Fix some inconsistent line endings in filesystem.c

This fixes the issue of the output being incorrect when outputting text over the serial connection. Part of #58
Catting large files and also the help function now outputs correctly every time:

swsh> ?                                                                                                   
Command List:                                                                                             
 ?      print command list                                                                                
 help   print command list                                                                                
 flash  reboot to UF2 bootloader                                                                          
 ls     usage: ls [PATH]                                                                                  
 cat    usage: cat <PATH>                                                                                 
 b64encode      usage: b64encode <PATH>                                                                   
 df     print filesystem free space                                                                       
 rm     usage: rm [PATH]                                                                                  
 format usage: format YES                                                                                 
 echo   usage: echo TEXT {>,>>} FILE                                                                      
 stress test CDC write; usage: stress [LEN] [DELAY_MS]

I have tested this on my sensorwatch pro using the serial connection and when in normal watch mode.

[Hylian]

It looks like you're retracing my steps in the original PR. 😛

Unfortunately, I don't recommend merging this PR, as we really should be servicing TinyUSB from outside the app loop context, as commented in the linked issue.

If you'd like to give it a shot yourself, I'd be happy to give pointers. Otherwise, I can try and find some time this week to put up a fix.

[madhogs]

It looks like you're retracing my steps in the original PR. 😛

Could you please explain what you mean, did you try these changes previously and they weren't needed?

Unfortunately, I don't recommend merging this PR, as we really should be servicing TinyUSB from outside the app loop context, as commented in the linked issue.

I agree that this doesn't fix the interactive use over the serial connection but these are both valid data loss bugs that need fixing, no? This pr does fix issues when outputting large amount of text.

If you'd like to give it a shot yourself, I'd be happy to give pointers. Otherwise, I can try and find some time this week to put up a fix.

I'm not sure I understand the required changes enough to implement it myself.
If you have time to put up a fix that would be amazing, the previous repo worked very well after your PR 😄 .