I wanted to give you some insight to the way you posted this. Far to many people post this way.
One needs to pull themselves out from where they are at and realize that the rest of us are not sitting right there with you. We know nothing of what you doing at all. So the best way to post something is to pretend you are not you but us. So you need to wright it that way.
I am trying to extend my i2c bus using the sparkfun differential i2c extender
Which one? no part number or even better a link to it.
connected via a pair of the extenders
and a cat5 cable,
How long is the run of cable?
all I get, after an initial pulsing, is a solid cyan led,
Initial pulsing??? What are you trying to do? what code are you running ??
which I believe can indicate incorrect i2c wiring with firmware trying to run i2c.
again, what code are you running? Did you try this same code without the I@c Extender and cat5 cable up close to see if it works that way?
Has anyone had any luck with these extenders and did you have to cut any of the jumpers to get it working.
I have use then and they work just fine, but not knowing which one you are using is hard to say. As for “cut the jumpers” you mean have to change the I2C address that all depends on if someone else needed to because that address interferes with some other address.
Now, I am NOT at all picking on you. I am just trying to show you our perspective when we read a post like this. To help you write posts looking at it from the receivers end, so you can get the best help.