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Altera_Forum's avatar
Altera_Forum
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9 years ago

custom i2c

Just after a quick/general comment as I am a bit new to HDL. I was struggling to get much over 30kHz on my i2c connection because my code on my Nios II processor was not handling the interrupts...
Altera_Forum's avatar
Altera_Forum
Icon for Honored Contributor rankHonored Contributor
9 years ago

Normally I think 1.5k Resistors as pull-ups should be enough. Also your drive strength is already high enough.

You have three options to try:

- change the pull ups to 1k and meassure again. Compare if the Signal is better or the same. Don't use less than 1k!

- Can you change the slew-rate to 2?

- Can you use a active '1' instead of 'Z' for bits which are really high on the bus. Use 'Z' for inactive, ACK and data-receive.

I once had also written an custom I2C-Core and I used '1' for all active high Bits generated by the master. As I remember, my bus also shows this "shark-fins" on edges from '0' to 'z' but not from '0' to '1'.