= nrfdude =

  nrfdude reads and writes flash on nRF24LU1+ devices using Nordic's
factory-programmed USB loader. This program may be used with with custom boards
or development kits, such as Sparkfun's nRF24LU1+ breakout (WRL-09034).

WARNING: this tool is for experienced embedded developers. Failure to read and
fully understand nRF24LU1+'s datasheet and nrfdude's operation can result in
non-operation and/or damnage. Recovery may not be possible without additional
tools, if at all.

  Unlike the better-known avrdude and Arduino platform, nrfdude is inflexible:

  - nrfdude is an immature tool (few options and not well vetted).
  - Firmware must be in Intel HEX format.
  - Only the main block, not the info block, can be written.
  - The nRF24LU1+ loader does _NOT_ have automatic reset.
  - The nRF24LU1+ loader is _NOT_ a "real" bootloader. It will not always
    run on power up!
  - Disabling the USB loader's main block readback function will break nrfdude.


= Building =

  libusb-1.0 is required. Edit "config.mk" if the included pkg-config based
configuration does not work on your platform. Make sure your system has
development headers and not just the binaries.

  While the code isn't complex and should compile and work on any *NIX machine,
only Linux (Ubuntu) on a 64 bit x86 has been tested.

  To build:

$ make

  To rebuild:

$ make clean all


= Usage =

 ---------------
 !!! WARNING !!!
 ---------------

  The nRF24LU1+ loader will not run on power up! The only way to get back into
the loader is to manually jump to it in your firmware! The entry point for the
loader on my particular chip is 0x7800. I highly recommend dumping your
device's firmware and confirming the loader's memory location before
continuing. Make sure your program always has a way to get back to the loader,
such as reading a switch, if you wish to continue using nrfdude.

  If your chip has a different loader location, then the nrfdude's write
protection will not work. Modify the source and recompile before continuing
use of nrfdude.

Usage: nrfdude [options]
Options:
 -h                    : This message
 -r <file>             : Read from device to <file>
 -w <file>             : Write from <file> to device
 -x                    : Allow writing to 0x7800-0x7FFF (bootloader)


= Notes =

  1. Reading/dumping firmware may produce a HEX file that is smaller than
     expected. Records that have unwritten flash (only 0xFF bytes) are not
     written out.

  2. Due to outside decisions, writing to flash is not the fastest or low-wear.
     Keep in mind the nRF24LU1+'s flash only has 1000 write cycles. Buy or
     build a few boards if you expect fast and repetitive development cycles.

  3. Write speeds may vary since nrfdude will not rewrite an unchanged flash
     page.

  4. Writes are implemented as a whole device read-modify-write operation. If
     nrfdude cannot read flash, then it cannot reliably write flash.