Hello,
I am trying to set two pins on the Cyclone III I'm using (EP3C120F780C7N) to work at 3.3V. I'm developing a custom slave I2C controller and the I2C bus will be 3.3V. I changed the pin assignments for this in the pin editor shown below.
33VPins.jpg
When I look at this communication link on the scope I see the microcontroller controlling the data bus at 3.3V when sending, but when the FPGA controls the data bus to send the level is only at 2.5 volts. The bus is pulled up to 3.3V with to 4.7k. The only lines of interest here are really SDA/SCL. When looking at the FPGA talk to the CPU you can see the level difference very clearly. From reading the documentation it seems that pins N26 and R27 should support 3.3V operation.
Any direction/guidance here?
I am trying to set two pins on the Cyclone III I'm using (EP3C120F780C7N) to work at 3.3V. I'm developing a custom slave I2C controller and the I2C bus will be 3.3V. I changed the pin assignments for this in the pin editor shown below.
33VPins.jpg
When I look at this communication link on the scope I see the microcontroller controlling the data bus at 3.3V when sending, but when the FPGA controls the data bus to send the level is only at 2.5 volts. The bus is pulled up to 3.3V with to 4.7k. The only lines of interest here are really SDA/SCL. When looking at the FPGA talk to the CPU you can see the level difference very clearly. From reading the documentation it seems that pins N26 and R27 should support 3.3V operation.
Any direction/guidance here?
