On Sat, 28 May 2005 16:38:31 +0200 Jean Delvare <khali at linux-fr.org> wrote: > Hi Fred, > > > I need to connect a compass having an i2c bus to a computer. The > > current plan is to use one of these i2c/parallel port adapters. > > However, I'm not sure if it will indeed work. Here is what I think > > at the moment. > > > > Many kernel drivers do support e.g. the Philips adapters. However, > > it seems that this is not to use the adapter externally. This would > > however work with the i2c-pcf-epp driver, but it hasn't been ported > > yet to linux 2.6 (I saw a more than 1 year old message on that on > > this list, but no follow up). > > There are two kinds of parallel port adapters which can be used to > control an I2C bus. > > The first kind uses the parallel port to address an external I2C > master, such as the Philips PCF8584. What goes through the parallel > port in this case are commands for the external master (and data > bytes, of course). That's what the i2c-pcf-epp driver does. But it hasn't been ported to linux-2.6 yet. > > The second, more popular kind controls the lines of an I2C bus > directly through the parallel port pins. In other words, the parallel > port is the I2C master itself. There are various implementations, some > use the same pin to read and write, others use different pins. That's > what the new i2c-parport drivers does. A long time ago (a year ago?) I have tried to plug it directly a suggested somewhere (can't remember) but it didn't work because of differences in levels (the compass wasn't pulling enough one of the ways if I remember well). > > In almost all cases you need to wire some electronic components > between the parallel port and the i2c client chip(s), except for the > i2c-pport driver (*not* the same as i2c-parport). > > > The doc for the i2c-parport kernel module gives the schematics of a > > diy "i2c-over-parallel-port" adapter. Anybody knows how easy it is > > to use? > > I'm not sure I get what your question really means. If you are able to > build the adapter as described, you get a fully controllable I2C bus. > The hard part is to build it. Once it's done, using it is just as easy > as using any other I2C or SMBus adapter under Linux. > > > Any suggestions? > > If you have the required electronics skills, simply build the adapter > according to the schematics of the i2c-parport documentation (second > one is better). Exactly what I needed to hear. Thanks. Fred
