Turn your Stellaris launchpad into an uart-spi bridge.
This project emerged from the need to replace an atmega328p used in a chinese clone of the AVR Transistortester (see https://www.mikrocontroller.net/articles/AVR_Transistortestester ) which i had toasted with a charged capacitor. Getting a new avr was no problem, but i had to program it and had no programmer or spare arduino. So i read around and found that an avr may be serially programmed via spi, and also found avrdude doing exactly this with numerous programming hardware. As i had a Stellaris launchpad lying around which i had gotten cheap on launch and also did some programming with it, i wondered if it would be possible to use this as programmer. Since it has a number of hardware spi interfaces and an debug link with integrated serial communication, it turned out to be quite easy to implement a bridge which streams data from the uart to the spi and back. I also forked avrdude from kcuzner because he already implemented an interface for avrdude that directly uses available spi interfaces, and my implementation would be quite similiar. You can find this fork at https://github.com/RJdaMoD/avrdude . Of course you may use this also for other spi communications with other ic's like flash, fpga... But my transistortester is working again:)
On connection, the icdi (integrated control and debug interface, i think) of a launchpad offers a serial connection to the target processor which your system might offer as ttyACM0 (linux) or COMx (windows), MacOS should be similiar. You can connect to this interface with the standard serial connection parameters 115200 baud, 8 bit, no parity and 1 stop bit, for example with gtkterm/hyperterm or similiar terminal software. stellarisSPI offers hex- and bin-mode, where the first is the default on powerup. In hex-mode, for each pair of characters forming a hexadecimal 8bit number the corresponding byte is sent on the spi-interface. The byte that is read back, is transferred to the host as hexadecimal number too. The interface may also be operated in bin-mode, where all data is transferred binary. The spi-interface is hardcoded to 8bit motorola master mode. CPOL and CPHA default to zero (which is correct for avr serial flashing), but may be changed by command. The clockspeed of the spi-interface is derived from the processor clock and defaults to 115200, but may also be changed. The used pins are PA2 = SCL, PA4 = MISO and PA5 = MOSI. The two pins PF1 and PF3 may be used as digital outputs which are controlled by commands. As they also drive two cathodes of the onboard rgb-led, their usage may be monitored. The command interface of stellarisSPI is a simple escape-key interface where a command character, defaulting to '$', lets the processor interpret the next character send from the host as command. If this is again the command character an dthe interface is in bin-mode, this character is actually sent over the spi. The supported commands are the following: 'f': If the next character is '0', '1', '2' or '3', the number is interpreted as two bits where CPOL is the lower bit, and CPHA the upper bit. The spi-interface is then set according to this configuration. 'F': If the follwing character is a 'b' or 'B', switch to bin-mode. If it is 'h' or 'H', switch to hex-mode. 'g': If the next character is a hexadecimal digit, it iss interpreted as four bits where the upper two bits form a bit mask, and the lower two bits the values for the two output pins PF1 (lower bit) and PF3 (upper bit). Thus 'A' means "set PF3 to 1", '4' means "clear PF1" etc. 's': This changes the speed of the spi-interface. If the next character is alpha-numeric, it is interpreted as a speed code where the sequence 0-9,A-Z,a-z forms indices (A=10,a=36...) that map on the following speed table: 50, 75, 110, 134, 200, 300, 600, 1200, 1800, 2400, // 0 - 9 4800, 9600, 19200, 38400, 57600, 115200, 230400, // A - G 460800, 500000, 576000, 921600, 1000000, 1152000, // H - M 1500000, 2000000, 2500000, 3000000, 3500000, 4000000 // N - S If instead a '' is encountered, the following characters up to the next '' are interpreted as a decimal number which sets the spi-speed. 'S': The same as above, but for the uart. As it seems that one can not reconfigure the icdi for other serial speeds than 115200, this command should not be used. 'C': The next character will be set as the command character if it is not an already defined command. If the arguments of the command characters have not the expected form, the whole character sequence is discarded.
The code comes as an eclipse project and was built using the TI driverlib (though only rom functions are used, so the include files are sufficient) and the summon arm toolchain. Startup code was taken from https://github.com/mroy/stellaris-launchpad-template-gcc Images are also included as hex and elf, which may be flashed on the launchpad using openocd or lm4flash. Debug contains image with full debug information and no optimization, whereas Release image has no debug info and full optimization.
You may do whatever you want with the code, but please keep a track to me. I will not provide any liabilities or warranties.