Monday, September 17, 2007
I2C + GM3 = problems
A while ago there was a discussion about using the I²C protocol for linking RepRap boards. My RepStrap machine uses I²C but when I started using it to control the GM3 gear motor of the extruder I ran into problems with electrical noise. Although I managed to solve them, my recommendation is that I²C is not a suitable protocol for off board communication, and the GM3 needs suppression. A triangle of three 1nF ceramic capacitors, one connected across the terminals and one from each terminal to the can works well and a couple of ferrite beads plus a fourth capacitor works even better.
More details in my blog:
hydraraptor.blogspot.com/2007/09/bus-stops
hydraraptor.blogspot.com/2007/09/dc-to-daylight
More details in my blog:
hydraraptor.blogspot.com/2007/09/bus-stops
hydraraptor.blogspot.com/2007/09/dc-to-daylight
Labels: DC motor suppression, GM3, i2c
Saturday, August 11, 2007
Looking forward
I've been trying to get one of my sample pic chips (18f2550) working using usb. Finally got it recognized and the driver installed. Amazing how many ways there are to wire so few pins. But in the course of my investigations I found some things that may be relevant to where the development team has stated where they want to go. There is a nice little USB to i2c project with linux/windows/mac support at
http://www.harbaum.org/till/i2c_tiny_usb/index.shtml
Seems a simple enough project to provide i2c directly to our devices. There are lots of i2c software out there that would have to be incorporated into whatever device is used for the controller. The other piece is jUSB which would provide the interface between Java and our i2c bus. There are linux and windows components for that referenced at
http://jusb.sourceforge.net/
Of course we could always just talk to our devices directly via usb, but having the i2c access would maybe be the more direct way of doing it. The controllers could still be usb programmable of course to facilitate updating. I like the booting via usb concept which eliminates needing a programmer except to get initial code into chips. But with something like rrrf and a base of reprappers that might eliminate the need for programmers except for those that want to do it themselves. I actually have to do it, but since I have a jdm programmer that works, I just added icsp to it and put connector on it and test circuit. Hopefully I can get to writing some actual software and download it now that I have the circuit recognized :)
Give me your thoughts, cheers and jeers. Happy reprapping :)
http://www.harbaum.org/till/i2c_tiny_usb/index.shtml
Seems a simple enough project to provide i2c directly to our devices. There are lots of i2c software out there that would have to be incorporated into whatever device is used for the controller. The other piece is jUSB which would provide the interface between Java and our i2c bus. There are linux and windows components for that referenced at
http://jusb.sourceforge.net/
Of course we could always just talk to our devices directly via usb, but having the i2c access would maybe be the more direct way of doing it. The controllers could still be usb programmable of course to facilitate updating. I like the booting via usb concept which eliminates needing a programmer except to get initial code into chips. But with something like rrrf and a base of reprappers that might eliminate the need for programmers except for those that want to do it themselves. I actually have to do it, but since I have a jdm programmer that works, I just added icsp to it and put connector on it and test circuit. Hopefully I can get to writing some actual software and download it now that I have the circuit recognized :)
Give me your thoughts, cheers and jeers. Happy reprapping :)
