Cyclone V HPS - I2C1 through FPGA routing

Ok, I got it running, here it is for future references and as an example to anyone who needs this:

The above are the four I2C signals used to interface to the FPGA and the output, NOT the 50MHz clock. The project generates the following interface:

-- I2C2 (FPGA)
hps_0_i2c2_clk_clk              : out   std_logic; -- I2C SCL Control Signal
hps_0_i2c2_out_data             : out   std_logic; -- I2C SDA Control Signal
hps_0_i2c2_sda                  : in    std_logic; -- SDA Input pin
hps_0_i2c2_scl_in_clk           : in    std_logic; -- SCL Input pin

The first two signals above are the control for the BUFIO that drives the output, while the signals below are the input signals from the pins. To correctly drive the output and read the signals in, I added the following process:

i2c2_proc: process(hps_0_i2c2_clk_clk, hps_0_i2c2_out_data)
begin
	
	if(hps_0_i2c2_clk_clk = '1') then
		I2C2_SCL <= '0';
	else
		I2C2_SCL <= 'Z';
	end if;

	if(hps_0_i2c2_out_data = '1') then
		I2C2_SDA <= '0';
	else
		I2C2_SDA <= 'Z';
	end if;
end process;

hps_0_i2c2_scl_in_clk <= I2C2_SCL;
hps_0_i2c2_sda <= I2C2_SDA;

The above is the equivalent of the image below, although the naming is confusing.

Once the project is generated, you MUST re-generate the QTS files, which will effectively set this line "1, /* I2C2USEFPGA */" in pinmux_config.h.

Also, to make sure your bootloader and Linux system recognise the new module, you need to explicitly add them to the drivers:

/* UBOOT */
&i2c2 {
	status = "okay";
	clock-frequency = <100000>;
	compatible = "snps,designware-i2c-17.0", "snps,designware-i2c";
	clocks = <&l4_sp_clk>;
	status = "okay"; /* embeddedsw.dts.params.status type STRING */
	clock-frequency = <100000>;
	i2c-sda-hold-time-ns = <100>;
	i2c-sda-falling-time-ns = <100>;
	i2c-scl-falling-time-ns = <300>;
};

/* Linux */
&i2c2 {
	status = "okay";
	clock-frequency = <100000>;
};

Recompile and test. Remember to add pullup resistors on the SDA and SCL lines.

Hope this helps.

Cheers,

Alberto