From mboxrd@z Thu Jan 1 00:00:00 1970 From: Andre Schwarz Date: Thu, 10 Apr 2008 14:17:33 +0200 Subject: [U-Boot-Users] I2C @ MPC8343 In-Reply-To: <47FE13F4.22909.A061CC@w.wegner.astro-kom.de> References: <47FDD1C6.3000205@matrix-vision.de>, <47F3F98010FF784EBEE6526EAAB078D10635DEF2@tq-mailsrv.tq-net.de> <47FE13F4.22909.A061CC@w.wegner.astro-kom.de> Message-ID: <47FE055D.5060901@matrix-vision.de> List-Id: MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: u-boot@lists.denx.de Wolfgang, I have indeed a LM75 on this bus - but it's not adressed. The same I2C bus works fine on linux-2.6.25 including LM75 and EEPROM. The oszi shows complete transactions with valid data. I think it is as software issue. Thanks, Andre w.wegner at astro-kom.de schrieb: > Hi, > > On 10 Apr 2008 at 13:08, Martin Krause wrote: > >>> After some tries (i2c md ..) the bus hangs and no more transactions >>> can >>> be seen on the bus. >>> >> One reason for a hanging bus could be a lost clock pulse. This could >> happen, if the low->high rise time of the bus signal is longer than >> the clock pulse width. For testing you could try a lower bus clock >> (10 kHz for example). >> > > sorry if I did not follow the discussion up to here. As I stumbled over > it yesterday, I just want to give another example how to hang a bus. > > There are devices (namely LM75) that claim to be I2C devices but > do not care about I2C specification. In case of LM75, a read must > always be 16 bit (2 bytes), in case of reading only 1 byte the device > does not interpret the missing ACK correctly and, in case the > last byte read is '0', it will block the bus until some more (worst > case 8) SCL pulses follow. > > Maybe something like this could also happen in your case? > > Regards, > Wolfgang > > MATRIX VISION GmbH, Talstra?e 16, DE-71570 Oppenweiler - Registergericht: Amtsgericht Stuttgart, HRB 271090 Gesch?ftsf?hrer: Gerhard Thullner, Werner Armingeon, Uwe Furtner -------------- next part -------------- An HTML attachment was scrubbed... URL: http://lists.denx.de/pipermail/u-boot/attachments/20080410/73f6157e/attachment.htm