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Hello!
This is regarding a prior discussion on the I2C communication. Previously I had issues with running CY8CKIT-042 as slave and CY8CKIT-040 as master with two different Creator versions (4.0 and 4.2), but it later got resolved with successive discussions in this forum. I would like to thank Bob and Moto for helping me in resolving the compatibility issues between the two kits.
Currently I am trying to interface CY8CKIT-040 (Master) with a video decoder (slave) that supports an serial MPU interface with a data rate of 400 kbps. I was able to set the data rate on the CY8CKIT-040 to 400 kbps by changing the IMO clock frequency to 32 MHz. But I am concerned about the internal pull up resistors that are already installed on the CY8CKIT-040, as the video decoder requires a 4.7 K resistor for proper operation.
Please advise on whether there is a way to disable these internal pull up resistors so that I can go ahead connecting the external video decoder to the CY8CKIT-040 with external pull up resistors (4.7 K).
Thanks and Regards,
Nandhini Jayapandian
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PSoC 4 Architecture
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Hi,
Usually I2C operates with pull-up resistor of 2K ~ 10K and 4.7K is a middle (safe?) range.
But what important is the ramp of rise and fall edge.
Please refer to the I2C specification
https://www.nxp.com/docs/en/user-guide/UM10204.pdf
Having written above, chance is high that with the 2.2K installed in the CY8CKIT-040, the slave can work.
I'd suggest you to connect the device and monitor the ramp to see if it is within the specification range.
(Or more casually, connect and try! I hope it will work...)
In case not, if the ramp is out of range, I would do (from easy to difficult)
(1) remove pull-up resistors if there is/are between the CY8CKIT-040 and the slave
(2) replace R8 and R9 of the CY8CKIT-040 with 4.7K
(3) use P3[0] and P3[1] for I2C pins and add external pull-up resistors
Note: (3) uses pins for SWD, so we need to set Debug select to GPIO,
with this we will not be able to debug the program.
moto
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Hi,
Usually I2C operates with pull-up resistor of 2K ~ 10K and 4.7K is a middle (safe?) range.
But what important is the ramp of rise and fall edge.
Please refer to the I2C specification
https://www.nxp.com/docs/en/user-guide/UM10204.pdf
Having written above, chance is high that with the 2.2K installed in the CY8CKIT-040, the slave can work.
I'd suggest you to connect the device and monitor the ramp to see if it is within the specification range.
(Or more casually, connect and try! I hope it will work...)
In case not, if the ramp is out of range, I would do (from easy to difficult)
(1) remove pull-up resistors if there is/are between the CY8CKIT-040 and the slave
(2) replace R8 and R9 of the CY8CKIT-040 with 4.7K
(3) use P3[0] and P3[1] for I2C pins and add external pull-up resistors
Note: (3) uses pins for SWD, so we need to set Debug select to GPIO,
with this we will not be able to debug the program.
moto