Just bought an I2C serial interface....$200 I think... >From: Trevor Page >Reply-To: pic microcontroller discussion list >To: PICLIST@MITVMA.MIT.EDU >Subject: Re: [PIC]: I2C sniffer >Date: Thu, 16 May 2002 15:46:16 +0100 > >Lawrence, > >I was recently asked to build an I2C monitor. > >My first approach was to use the Philps PCF8584 I2C / parallel interface >chip. This IC has a special monitor mode, which is very convenient if you >wish to implement a basic 100KHz bus monitor. Wire it up to a 16F877 or >something to send the data via RS232, and there you go. It's not the best >monitor in the world - personally there are a few things I don't like the >8584 chip. For instance, IIRC the 8584's interrupts cannot be used when in >monitor mode, which is plain stupid (I could be wrong on that detail, but I >remember it was something like that). I think you end up having to waste >lots of processor time polling a bit instead to check on activity... >something like that. I think this is all to do with the fact that the >monitor mode was really an afterthought on the 8584. > >The 8584 is rated for bus speeds up to 100KHz but a friend of mine has >claimed that his PCF8584-based monitor circuit worked perfectly well on a >400KHz bus. > >I also implemented a monitor using just a fast AVR, with some external >logic >(flipflops + inverters) to detect start / stop conditions. I used a USBMOD2 >USB interface to pipe the data to the PC. My intention was to produce a >better 400KHz monitor without using the PCF8584 - but this was surprisingly >difficult to do using a mid-range AVR. Given the chance, I'd probably do it >again using a Ubicom (Scenix) processor, or with a CPLD or something. In >fact the reason I tried the AVR approach and ditched the 8584 was because I >never believed it would work reliably at 400KHz since the datasheet clearly >states that it goes 100KHz tops - I was gutted when my friend proved me >wrong, but there you go ;o) > >I reckon the easiest approach might be to take a PCF8584 and maybe wire >it's >parallel interface directly to your PCs parallel port, and write a nice >Windows monitor application? Erm.. maybe that's what I should have done :) > >Regards > >Trevor. > > > > > > -----Original Message----- > > From: Lawrence Lile [SMTP:llile@TOASTMASTER.COM] > > Sent: 16 May 2002 15:24 > > To: PICLIST@MITVMA.MIT.EDU > > Subject: [PIC]: I2C sniffer > > > > On an analog scope, a burst of I2C data looks like a stream of bullets. > > After beating my head against the lab bench during the last encounter >with > > I2C, I've concluded that one needs an I2C sniffer to really troubleshoot > > one > > of these systems. (Unless of course one has a $10,000 scope ;-) This > > would > > be a passive beast that would sit on the I2C bus and report when it sees >a > > start bit, address, ACK or data, and also report which is which. I >could > > imagine sending the info out over an RS232 line, and also displaying it >on > > a > > 4-line LCD, since a lot of conversations on an I2C bus might be pretty > > short. Didn't find any such animal in the PIClist archives. Has >anybody > > looked into this? > > > > > > -- Lawrence Lile > > Sr. Project Engineer > > Salton inc. Toastmaster Div. > > 573-446-5661 Voice > > 573-446-5676 Fax > > > > -- > > http://www.piclist.com hint: To leave the PICList > > mailto:piclist-unsubscribe-request@mitvma.mit.edu > > > >-- >http://www.piclist.com hint: To leave the PICList >mailto:piclist-unsubscribe-request@mitvma.mit.edu _________________________________________________________________ MSN Photos is the easiest way to share and print your photos: http://photos.msn.com/support/worldwide.aspx -- http://www.piclist.com hint: To leave the PICList mailto:piclist-unsubscribe-request@mitvma.mit.edu