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Adventurer
Adventurer
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Registered: ‎01-26-2017

KCU105 - setup I2C for IIC Mux 1 (PCA9544)

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Hi,

 

I have a working I2C module in hardware on my board for programming the ADV7511 chip. This works fine, as the I2C path to ADV7511 goes through TCA9548 8-channel bus switch.

 

However, my design now requires that I use I2C to program another device also, which is plugged in FMC-HPC. I assume that FMC pins c30 and c31 are wired directly to the I2C chips, so all I should have to change is the address (from 0x74 to 0x75) and write data XXXXXX00 (X is don't care) then I should be able to access the other device's registers. However nothing happens. 

 

To debug, I set my I2C module to spam the FMC pins with continuous instructions and measure the pins with an oscilloscope. SDA and SCL are always pulled high, which leads me to believe that the connection to FMC is not working for some reason. I.e the path is maybe still going through the TCA9548 8-channel bus switch instead of the PCA9544 4-channel bus switch.

 

Could anyone provide any insight into anything I might have missed?

 

Thanks for your time,

Aaron

--- Estimated Development time: 2*Pi*(planned completion date) ---
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Contributor
Contributor
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Registered: ‎04-27-2016

From PCA9544 datasheet:  "The three LSBs of the control byte are used to determine which channel (or channels) is to be selected." Moreover, the I2C bus from FMC HPC connector is routed to channel 1 of U80 (PCA9544, 0x75).  So write XXXX101 to enable channel 1 of PCA9544 bus switch.

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Contributor
Contributor
1,498 Views
Registered: ‎04-27-2016

From PCA9544 datasheet:  "The three LSBs of the control byte are used to determine which channel (or channels) is to be selected." Moreover, the I2C bus from FMC HPC connector is routed to channel 1 of U80 (PCA9544, 0x75).  So write XXXX101 to enable channel 1 of PCA9544 bus switch.

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Adventurer
Adventurer
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Registered: ‎01-26-2017

Okay, will try this and report back - thanks.

--- Estimated Development time: 2*Pi*(planned completion date) ---
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Adventurer
Adventurer
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Registered: ‎01-26-2017
Yup, that worked. Much thanks (although I think I should have realised such a simple mistake myself >.< )
--- Estimated Development time: 2*Pi*(planned completion date) ---
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