Since our robotics kit uses an I2C bus, it would be really handy for me to have a USB-to-I2C adapter. With the addition of a simple RJ11 adapter, I’d be able just plug in a module and start hacking on it without the annoying set-up times, that involve sorting out the Slug and power board combo. If Student Robotics had several of these adapters, then any member could just grab a module and start hacking on some code.
i2c-tiny-usb:
I’ve just come across Till Harbaum’s i2c-tiny-usb design. Rather surprisingly this uses a relatively cheap ATtiny45 Atmel AVR and nothing else. It bitbangs the USB protocol. Apparently, this works rather well. What’s even more exciting, is that there’s a kernel driver available for the i2c-tiny-usb. This makes it behave as a proper Linux i2c bus device, so interacting with it from software couldn’t be simpler. This board can be an I2C master with clock speeds of up to 50KHz.
OSIF
The Open Source InterFace (OSIF) is part of the OpenServo project, and I believe was designed by Barry Carter. Carter took the i2c-tiny-usb design, and adapted it to use an AVR with more pins, and upped the maximum I2C clock speed to 400KHz. Furthermore, the board has support for serial (I think UART), 6 GPIO lines and an ADC channel. Barry Carter sells the OSIF for £20 a board.
Carter also provides a kernel driver for the OSIF as well :-D
I bought an OSIF earlier today. I like the way that the OSIF uses work from two previous open hardware projects to create
- 0830: Received a text from Tom containing a highly compressed set of questions relating to the power board. Set about answering them when I got up.
- Processed some paperwork.
- Worked on Farnell screen scraping – progressing nicely. Some nasty problems involving Unicode strings getting munged about though.
- Read about John’s escapades.
- Had some xbee related conversations with Phil. Sadly massively diverged into setting up his ssh config.
- The random period of immense internet laggyness started early today. Around 7pm I guess. Moaned profusely.
- Performed a very short investigation investigation into radio modules for general stuff-monitoring projects. Decided that the CC2420 might be good – but a little expensive (~£5 a chip from Farnell). Will continue search for cheaper alternatives. Would be good to produce a large number of devices that use them.
- Looked for an extension lead casing manufacturer. Was pretty unsuccessful. Wanted to find an extension lead casing with space for some extra electronics in it…
args = re.sub( r"/usr/lib/libpng12.so", "", args )
s = subprocess.Popen( "/home/rob/ecssr/proj-svn/slug/init-br/build_armeb/staging_dir/bin/armeb-linux-uclibc-g++-orig " + args ,
stdout=subprocess.PIPE,
shell = True )
I just finished sorting out using the toolchain for the PWM board. Problem with the toolchain that I had was that the binutils I had installed (2.16) doesn’t support the MSP430F2013. After some searching around I found the patch I needed to apply to binutils in mspgcc CVS – and then managed to find a post about it on the mailing list.
Once the toolchain was built I ran a simple program that toggled the output pins continuously:
#include <msp430x20x3.h>
static int i = 0;
int main( void )
{
WDTCTL = WDTHOLD | WDTPW;
P1SEL = 0;
P1DIR = 0xFF;
while(1)
{
P1OUT ^= 0xFF;
}
}
The program ran correctly, and the level translation between the MSP430 and the servo outputs worked nicely. Good. Only motor controller to go now, and then we’ll be living in a softwarey world. Ah yes – the TI USB UIF interface seems to be working perfectly in spy-bi-wire mode :-)
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