Python nRF51 DFU Server

A python script for bluez gatttool using pexpect to achive Device Firmware Updates (DFU) to the nRF51.
The host system is assumed to be some flavor of Linux, and was developed with the Raspberry-Pi as the primary hosting system.

NOTE:
This is probably not a beginner's project.
Peripheral firmware updating is a complex process, requiring several critical development support steps, not covered here, before the dfu.py utility can be used.

It is assumed that your peripheral firmware has been build to Nordic's SDK8.x + SoftDevice 8.x
The target peripheral firmware should also include some variation of Nordic's DFU support.

How you get the target periheral to enter DFU-mode (e.g. advertizing DfuTarg) is not handled here.
It is assumed you can trigger your peripheral to enter the bootloader; either by a hardware switch or application-trigger.

The dfu.py utility comes into play only after the peripheral is executing the bootloader.

System:

• Raspberry Pi - RaspberryPi B+ or later (tested with RaspPi B+)
• Bluetooth 4.0 USB dongle - (tested with "UTechSmart" and "Plugable" BLE dongles)
• Linux raspian - kernel 3.12.22 or later
• bluez - 5.4 or later

See here for details on building bluez.

This project assumes you are developing on a Linux/Unix or OSX system and deploying to a Raspberry Pi (Raspian) system. Development on Windows systems should be OK, but it hasn't been (nor will be) tested.

Prerequisite

sudo pip install pexpect
sudo pip install intelhex

Firmware Build Requirement

• Your nRF51 firmware build method will produce either a firmware hex or bin file named application.hex or application.bin. This naming convention is per Nordics DFU specification, which is use by this DFU server as well as the Android Master Control Panel DFU, and iOS DFU app.
• Your nRF51 firmware build method will produce an Init file (aka application.dat). Again, this is per Nordic's naming conventions.

The gen_dat Utility

The gen_dat utility will read your build method's hex file and produce a dat file. The utility is written the C-language, but should be easy to rebuild: just follow the directions at the top of the source file. Ideally, you would incorporate the gen_dat utility into your build system so that your build method will generate the dat file for each build.

Below is a snippet showing how you might use the gen_dat utility in a makefile. The application.mk file shows a more complete example. This makefile example shows how the gen_dat and zip files are integrated into the build process. It is an example, and you must customize it to your requirements.

GENZIP   := zip
GENDAT   := ./gen_dat

# Create .dat file from the .bin file
gendat: 
    @echo Preparing: application.dat
    $(NO_ECHO)$(GENDAT) $(OUTPUT_BINARY_DIRECTORY)/application.bin $(OUTPUT_BINARY_DIRECTORY)/application.dat 

# Create .zip file from .bin and .dat files
genzip: 
@echo Preparing: $(OUTPUT_NAME).zip
-@$(GENZIP) -j $(OUTPUT_BINARY_DIRECTORY)/application.zip $(OUTPUT_BINARY_DIRECTORY)/application.bin $(OUTPUT_BINARY_DIRECTORY)/application.dat

Usage

There are two ways to speicify firmware files for this OTA-DFU server. Either by specifying both the file with the dat file, or more easily by the zip file, which contains both the hex and dat files.
The new "zip file" form is encouraged by Nordic, but the older hex+dat file methods should still work.

Usage Examples

> sudo ./dfu.py -f ~/application.hex -d ~/application.dat -a EF:FF:D2:92:9C:2A

or

> sudo ./dfu.py -z ~/application.zip -a EF:FF:D2:92:9C:2A  

To figure out the address of DfuTarg do a 'hcitool lescan' -

$ sudo hcitool -i hci0 lescan  
LE Scan ...   
CD:E3:4A:47:1C:E4 DfuTarg  
CD:E3:4A:47:1C:E4 (unknown) 

Example of dfu.py Output

pi@raspberrypi ~/src/ota-dfu/ $ sudo ./dfu.py -z application_debug_1435008894.zip -a EF:FF:D2:92:9C:2A
DFU Server start
unzip_dir: /tmp/application_debug_1435008894_nzjesh
input_setup
bin array size:  72352
scan_and_connect
dfu_send_image
[0, 0, 0, 0, 0, 0, 0, 0, 160, 26, 1, 0]
Sending hex file size
oper: RESPONSE, proc: START, status: SUCCESS
dfu_send_info
PKT_RCPT:      200
PKT_RCPT:      400
PKT_RCPT:      600
PKT_RCPT:      800
PKT_RCPT:     1000
PKT_RCPT:     1200
PKT_RCPT:     1400
PKT_RCPT:     1600
PKT_RCPT:     1800
PKT_RCPT:     2000
PKT_RCPT:     2200
PKT_RCPT:     2400
PKT_RCPT:     2600
PKT_RCPT:     2800
PKT_RCPT:     3000
  ...
  ...
  ...
PKT_RCPT:    69800
PKT_RCPT:    70000
PKT_RCPT:    70200
PKT_RCPT:    70400
PKT_RCPT:    70600
PKT_RCPT:    70800
PKT_RCPT:    71000
PKT_RCPT:    71200
PKT_RCPT:    71400
PKT_RCPT:    71600
PKT_RCPT:    71800
PKT_RCPT:    72000
PKT_RCPT:    72200
State timeout
DFU Server done

NOTE:
The final "State timeout" is due to the target peripheral rebooting, as expected, and the disconnect not getting back soon enough.
This is benign: the update should have been successful and the peripheral should have restarted and run the new firmware.