Merged in zpl's changes. The FTP server is not yet reliable, in
particular trying to delete a file via FTP after copying another may
result in the Duet rebooting due to the webserver module getting stuck
in a spin loop. Also the copied file has on one occasion been observed
to be shorter than the original.
Incoming network requests can now span multiple TCP messages. Max upload
buffer increased to 2048. Also return layerHeight and generatedBy values
when asking for fileinfo on a gcode file. This is an interim commit that
needs cleaning up before release.
1. Reworked network layer to be more robust in the presence of network
errors (hopefully). In particular, don't release transmit buffers if
they might still be needed to retry sending data because the ACK got
lost.
2. Fixed bug whereby fileinfo command looked for the print height and
filament used if the extensio was .gcode or .gc or .gco but not if it
was .g.
3. When the M25 (pause print) command is received, pause the current
gcode so that commands such as M116 (wait for temperatures) can be
interrupted.
Rewrote the web server command parsing as a state machine. Added support
for persistent connections, used for file uploading. Changed file upload
protocol to pass status information back. Added web message type for
deleting files.
Added new request code rr_data for file uploading, and made other
changes to improve file upload speed.
Implemented S parameter to M208 command, to allow the negative limits of
axes to be set. Also reports current limits of no X/Y/Z parameter.
Reduced max reported free buffer size to 950 bytes to avoid problems
with file upload from Windows 8.1.
Reduced block read size when retrieving file info to work around an
intermittent bug that causes the SDHC card/ FATfs stack to return data
from the wrong sector sometimes. Tidied up some other code.
Added new variable "extr" in Json response to report extruder positions
Added new fileinfo request type, returns file size, object height, and
total filament needed (if available)
Fixed bug in returning last command response in Json response
Disable interrupts when adding/removing network request structs from
linked lists, in case lwip does callbacks from ISR contexts
Completed changes to support multiple concurrent HTTP file requests.
Added support for new poll response for future support of additional
heaters and multiple extruders. Fixed a bug in reporting extruder
distance.
Removed file httpd.c and moved its functions into Network.cpp. This
gives us type-checking across more interface boundaries and eliminates a
number of global functions. Also removed unused files fs.c, fsdata.c,
httpd-original.c.
Changed webserver and network code to support multiple concurrent
connections
Removed support for differential-mode ultrasonic z-sensor
Reduced X and Y instantDv from 15 to 10 mm/sec to allow outlines of
holes to e drawn at lower speed
Changed temperature reading code to give thermistor disconnected reading
of -273C when there is a negative high ADC offset correction
