Raspboot is a light-weight utility for loading binaries and interacting with memory on the Raspbery Pi. All communication is currently done over the serial port (UART) to keep the application small. I plan to add support for communicating over Ethernet at a later point, however my focus is on completing the core featues needed for my own development. (See the TODO list below)
Raspboot is intended for bare metal development on the Pi. It won't be able to load a Linux kernel, for example, nor would there be any benefit to doing so even if it could. The main reason to use Raspboot is that eliminates the need to reflash the Pi's SD card each time a code change is made. Raspboot can be used to transfer the program binary over a serial connection and load it directly into the Pi's memory, shortening turn-around times when testing code. A variety of other useful commands are planned, such as memory and register dumps.
The project is currently in its infancy; the version currently in the repository can only be used to upload binaries to the device. The interactive mode for entering commands is still incomplete, however I plan to commit it by the end of the week.
Raspboot uses a client/server model. The Raspberry Pi runs a server application and a Linux machine runs the client. Commands are entered via the client application, which sends them over a serial connection to the server. The server performs the command and sends back a reply if neccessary.
To compile code for the Raspberry Pi, the system needs to have the arm-none-eabi toolchain installed. On Debian/Mint/Ubuntu this can be installed via the package manager, e.g. apt-get install gcc-arm-none-eabi.
Raspboot can be compiled by running make in the checked out directory. The Makefile will build both the client (bin/raspboot) and server (bin/raspboot-server) applications. Running make install will install the Raspboot client binary to /usr/local/bin.
A Doxygen configuration file is included in the root directory of the project. Running make doc will compile the in-source documentation to the ./doc directory. make clean_doc can be used to delete the documentation files.
The server binary needs to be written to the Raspberry Pi's SD card and set as the bootable image. To do so, copy the server application to the boot partition of the SD card and add kernel=raspboot-server to the end of the config.txt file in the same directory. Once this is done, the card can be reinserted in the Raspberry Pi and the device powered on.
To transfer a binary with Raspboot:
raspboot -b /path/to/binary.bin -l 0x16000 /dev/ttyUSB0
The -b argument indicates which binary file to tranfer, -l is the location in the Pi's memory to upload the binary and the final argument is the serial port to open a connection to.
The current client runs in a loop, so if the uploaded binary terminates and returns out properly, it should jump back into the Raspboot server. Another binary can then be uploaded using the same command. Note that Raspboot will stack registers r0 through r12 and the link register (r14) before branching to the uploaded code.
Raspboot can be configured with the following arguments, all of which are optional:
-b Path to the binary file to upload [default: none]
-g Jump into the uploaded binary as soon as the upload finishes [default: disabled]
-t Terminate Raspboot after running the binary (typically used with -g) [default: disabled]
-h Print usage information if no other args are specified
-l The memory location to write the binary to [default: 0x10000]
-r The baud rate, as listed in the termios docs, e.g. 4800, 9600, 115200 [default: 115200]
-v The verbosity level. Errors = 0, Warnings = 1, General Info = 2. [default: 2]
If the -t command is not specified, Rasboot will enter interactive mode after uploading the binary file (if any). The following commands are available (optional parameters listed in [square brackets]):
get -l loc [-c count] Reads and prints 'count' bytes from 'loc'. 'count' defaults to 4 bytes.
set -l loc [-v value] Sets the contents of memory at 'loc' to 'value'. 'value' is a byte; the default is 0.
setw -l loc [-v value] Sets the contents of memory at 'loc' to 'value'. 'value' is a word; the default is 0.
go [-l loc] Executes code at 'loc'. Defaults to the value passed over the command line.
help Lists available commands
quit Exits Raspboot
Arguments can be passed in any order, e.g. both get -l 0x10000 -c 12 and get -c 12 -l 0x10000 are valid.
- Optionally pass parameters to the binary when executing it
- Finish interactive mode
- Switch to using
getoptfor interactive mode command parsing - Add Ethernet support (long term)
- GitHub Wiki documentation (long term)
It should be relatively straightforward to port the device server to a different platform. The only portion of the code that is specific to the Raspberry Pi is the serial port interface.
Both the Raspboot server and client are distributed under The MIT License.