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PSoC 4 MCU

Anonymous
Not applicable
‎Jun 12, 2017 05:58 AM

I2C Voltage Level 1.8V on Pins 12.0 and 12.1

I work with a CY8C4248BZI-L489 (PSoC 4200L) with the following top design:

   
        
  • SCB block configured as I2C (Mode Master, Data rate 50, Slew Rate Fast)
    •     
  • I2C_SCL assigned to Pin 12.0
    •     
  • I2C_SDA assigned to Pin 12.1
    •     
  • Both lines are pulled-up with external resistors (1.5k) to 1.8V
    •    
   

I found out that I cannot use the I2C with this setup as it expects a bus voltage of 3.3V (default). Is this correct? At least I2CM_scl_Read() returns 0 although it should be pulled-up.

   

Then I tried to change the bus voltage to 1.8V in the I2CM block settings. The docs say (top of page 21 SCB datasheet) that it's possible only with slew rate set to I2C FM+ and a data rate above 400. So I changed the data rate to 1000 and the slew rate to I2C FM+. It allowed me to set the bus voltage to 1.8V. The fitter then returns an error complaining that Pins 12.0 and 12.1 do not support OVTIO.

   

The pins are fixed - I cannot relocate them at the moment. I guess pulling-up to 3.3V would work but are there any solutions to using 1.8V?

   

Many thanks in advance.

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Anonymous
Not applicable
‎Jun 13, 2017 12:54 AM

Re: I2C Voltage Level 1.8V on Pins 12.0 and 12.1

I have added a sample project and an image with how the pull-up is done on our hardware:

   

I2C-Board-Test.cydsn__0.zip
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Vasanth
Moderator
Moderator
‎Jul 02, 2017 01:33 AM

Re: I2C Voltage Level 1.8V on Pins 12.0 and 12.1

Hi,


You need to use Reference generator fature of SIO pins.You need toset proper values in registers PAIR_VREF01_SEL and PAIR_VOH01_SEL bits . Description about them is given in these documents- http://www.cypress.com/file/218741/download (page#72-73) http://www.cypress.com/file/219506/download (page#1446)

Best Regards,
VSRS

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