1-Can I use FPGA, just as a wire, to carry a bidirectional line like I2C SDA from one pin of the FPGA to the other pin of the FPGA. In the FPGA there will not be an i2c master or slave it will just route the signal from one side to the other side. Both of the sides should be able to drive the SDA signal(bidirectional) WHY : I2c master and i2c slave is not physically connected to each other on the PCB BOARD. But they are physically connected to FPGA (Cyclone II EP2C20F484C8)

Dear Josyb. You answer is digitally appropriate :) Could you guide me on this. Is there an IO buffer in altera like in Xilinx? Do I need to use Megafunction?

I don't know about Xilinx - wouldn't touch it with a bargepole :) I use a component in my VHDL code: LIBRARY altera; USE altera.altera_primitives_components.all; .... odsda : opndrn port map ( a_in => dp_SDaOut , a_out => Sda ) ; Don't know how to do this in Verilog - wouldn't touch that with a bargepole either :)

Not sure that can work for bidirectional data. Any kind of buffer has to know the data direction.

--- Quote Start --- Yes, you can --- Quote End --- Unfortunately, I have to contradict. All existing physical level I2C repeaters or level converters are based on special hardware features, please review the respective datasheets. A similar function can't be implemented with regular FPGA IOs as far as I understand. A repeater on a logical protocol level would be possible, but not an easy design. P.S.: --- Quote Start --- Any kind of buffer has to know the data direction. --- Quote End --- That's exactly the point.

Yes No question (Using FPGA as a wire) | Altera Community

14 Replies

Altera_Forum
Honored Contributor
13 years ago
Listen to FvM; "A repeater on a logical protocol level would be possible, but not an easy design".

Your repeater needs to "listen" to the protocol and determine which direction the data is flowing. I've been through this exericse and determined that an FPGA I2C repeater is not worth the effort. Find another way.
Altera_Forum
Honored Contributor
13 years ago
Been there done that and dropped it as well. Not worth it. The only way is to actually decode the data and then determine what to do. No way to do a physical connection through the FPGA.
Altera_Forum
Honored Contributor
13 years ago
May be the above discuss can be indicated as: external I2C master<--->FPGA I2C slave-----FPGA I2C master<---> external I2C slave. Like a protocol converter.
Altera_Forum
Honored Contributor
13 years ago
--- Quote Start ---
May be the above discuss can be indicated as: external I2C master<--->FPGA I2C slave-----FPGA I2C master<---> external I2C slave. Like a protocol converter.
--- Quote End ---

The description fits in terms of involved effort, but not for the exact functionality.
The converter needs to pass the response of addressed peripherals from second bus immediately bit by bit, clock cycle accurate.

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Yes No question (Using FPGA as a wire)

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