Hi All, SPI is more simplistic in internal IC hardware design than I2c. If the SPI data bus receive garbage (spikes or noise) you can pull the chip select high and start clocking the data in/out again. SPI has /CS chip select Clock Data out Data in I2C has Clock Data Question ======== If an I2C bus receives garbage, how does one tell a I2C receiver to "reset" and start again, as there is only a clock and data line. Thanks in Advance. Joe
I2C vs SPI
Started by ●February 8, 2010
Reply by ●February 8, 20102010-02-08
"Joe G (Home)" <joe.g@optusnet.com.au> wrote in message news:4b6fecc1$0$3003$afc38c87@news.optusnet.com.au...> Hi All, > > SPI is more simplistic in internal IC hardware design than I2c. If theSPI> data bus receive garbage (spikes or noise) you can pull the chip selecthigh> and start clocking the data in/out again. > > SPI has > /CS chip select > Clock > Data out > Data in > > I2C has > Clock > Data > > Question > ======== > If an I2C bus receives garbage, how does one tell a I2C receiver to"reset"> and start again, as there is only a clock and data line.By generating a premature stop condition. Meindert
Reply by ●February 8, 20102010-02-08
Meindert Sprang schrieb:>> If an I2C bus receives garbage, how does one tell a I2C receiver to > "reset" >> and start again, as there is only a clock and data line. > > By generating a premature stop condition....and if one of the devices eventually blocks the bus with SDA=low (this can happen when a read access is aborted), apply SCL pulses until SDA goes high. Tilmann
Reply by ●February 8, 20102010-02-08
Tilmann Reh wrote:> Meindert Sprang schrieb: > >>> If an I2C bus receives garbage, how does one tell a I2C receiver to >> "reset" >>> and start again, as there is only a clock and data line. >> By generating a premature stop condition. > > ...and if one of the devices eventually blocks the bus with SDA=low > (this can happen when a read access is aborted), apply SCL pulses until > SDA goes high. > > TilmannThe correct way to RESET the I2C buss, is to do a repeat-START, then a STOP. Works every time. don
Reply by ●February 9, 20102010-02-09
don schrieb:> The correct way to RESET the I2C buss, is to do a repeat-START, then a STOP.Please note that you simply can't apply a (repeated) start condition when a device continuously holds SDA low. In such cases, you first have to provide SCL pulses until SDA gets high again, then do start-stop. Tilmann
Reply by ●February 9, 20102010-02-09
Tilmann Reh wrote:> don schrieb: > >> The correct way to RESET the I2C buss, is to do a repeat-START, then a STOP. > > Please note that you simply can't apply a (repeated) start condition > when a device continuously holds SDA low. In such cases, you first have > to provide SCL pulses until SDA gets high again, then do start-stop. >_If_ it lets go at all. I've seen cases where it didn't and a power cycle was required :-( -- Regards, Joerg http://www.analogconsultants.com/ "gmail" domain blocked because of excessive spam. Use another domain or send PM.
Reply by ●February 9, 20102010-02-09
In article <7tedm4Fam1U1@mid.individual.net>, invalid@invalid.invalid says...> Tilmann Reh wrote: > > don schrieb: > > > >> The correct way to RESET the I2C buss, is to do a repeat-START, then a STOP. > > > > Please note that you simply can't apply a (repeated) start condition > > when a device continuously holds SDA low. In such cases, you first have > > to provide SCL pulses until SDA gets high again, then do start-stop. > > > > _If_ it lets go at all. I've seen cases where it didn't and a power > cycle was required :-(Especially if the slave device is doing a clock stretch, holding SCL low. -- Paul Carpenter | paul@pcserviceselectronics.co.uk <http://www.pcserviceselectronics.co.uk/> PC Services <http://www.pcserviceselectronics.co.uk/fonts/> Timing Diagram Font <http://www.gnuh8.org.uk/> GNU H8 - compiler & Renesas H8/H8S/H8 Tiny <http://www.badweb.org.uk/> For those web sites you hate
Reply by ●February 9, 20102010-02-09
Paul Carpenter wrote:> In article <7tedm4Fam1U1@mid.individual.net>, invalid@invalid.invalid > says... >> Tilmann Reh wrote: >>> don schrieb: >>> >>>> The correct way to RESET the I2C buss, is to do a repeat-START, then a STOP. >>> Please note that you simply can't apply a (repeated) start condition >>> when a device continuously holds SDA low. In such cases, you first have >>> to provide SCL pulses until SDA gets high again, then do start-stop. >>> >> _If_ it lets go at all. I've seen cases where it didn't and a power >> cycle was required :-( > > Especially if the slave device is doing a clock stretch, holding SCL low. >Sort of the eternal stretch :-) I like SPI a lot more although I2C does have the advantage of being able to hang it all onto the same serial bus. But that can at the same time cause hang-ups while SPI never hung on me. -- Regards, Joerg http://www.analogconsultants.com/ "gmail" domain blocked because of excessive spam. Use another domain or send PM.
Reply by ●February 10, 20102010-02-10
Paul Carpenter schrieb:>> >> The correct way to RESET the I2C buss, is to do a repeat-START, then a STOP. >> > >> > Please note that you simply can't apply a (repeated) start condition >> > when a device continuously holds SDA low. In such cases, you first have >> > to provide SCL pulses until SDA gets high again, then do start-stop. >> > >> >> _If_ it lets go at all. I've seen cases where it didn't and a power >> cycle was required :-( > > Especially if the slave device is doing a clock stretch, holding SCL low.I have always carefully selected only such I2C slaves that don't do clock stretching... :-) Tilmann
Reply by ●February 12, 20102010-02-12
"Joe G (Home)" <joe.g@optusnet.com.au> wrote in message news:4b6fecc1$0$3003$afc38c87@news.optusnet.com.au...> Hi All, > > SPI is more simplistic in internal IC hardware design than I2c. If the > SPI data bus receive garbage (spikes or noise) you can pull the chip > select high and start clocking the data in/out again. > > SPI has > /CS chip select > Clock > Data out > Data in > > I2C has > Clock > Data > > Question > ======== > If an I2C bus receives garbage, how does one tell a I2C receiver to > "reset" and start again, as there is only a clock and data line. > > Thanks in Advance. > > Joe > >Thanks all for your comments. Joe