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I2C and SPI on one chip

 
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40inD



Joined: 30 Jul 2007
Posts: 112
Location: Moscow, Russia

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I2C and SPI on one chip
PostPosted: Fri Nov 28, 2008 12:50 am     Reply with quote
Is it possible to implement SPI and i2c on one chip? I want to read and write several devices on I2C bus and log data to MMC card. I think that in this case SPI can be software?
PCM programmer



Joined: 06 Sep 2003
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PostPosted: Fri Nov 28, 2008 8:50 am     Reply with quote
The MMC card is SPI. It's better to use hardware SPI with it.
Use another pair of general purpose i/o pins to do software i2c for the
i2c chips.

Use setup_spi(), spi_write(), spi_read(), etc., for the hardware SPI.

Use a #use i2c() statement to define the software i2c channel.
asmallri



Joined: 12 Aug 2004
Posts: 1635
Location: Perth, Australia

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Re: I2C and SPI on one chip
PostPosted: Fri Nov 28, 2008 10:26 am     Reply with quote
40inD wrote:
Is it possible to implement SPI and i2c on one chip? I want to read and write several devices on I2C bus and log data to MMC card. I think that in this case SPI can be software?


If you have external logic available then they could share a common bus. Use the MMC chip select line to disable the clock line to the I2C bus. When the MMC card is selected no I2C clock is fed to the I2C peripherals.
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Franck26



Joined: 29 Dec 2007
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Location: Ireland

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PostPosted: Fri Nov 28, 2008 5:10 pm     Reply with quote
Or you can use a pic with 2 MSSP so you will be able to use the SPI and I2C hardware at the same time.

Good luck,
Franck.
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