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Jacob11's avatar
Jacob11
Icon for Occasional Contributor rankOccasional Contributor
3 years ago

Nios 2 I2c timeout altera_avalon_i2c.c - timeout never occurs

Hi gang. I am using the altera avalon i2c driver for communication to peripheral devices on my board. I want to read from different i2c addresses to determine if a device is present. For ins...
tehjingy_Altera's avatar
tehjingy_Altera
Icon for Regular Contributor rankRegular Contributor
3 years ago

Hi Jacob


The feature that you are looking for is the i2c probe.

Unfortunately the library does not support this feature.


As for the addressing, did you change the addressing mode from 7Bit to 10Bit addressing?

You could search for "ALT_AVALON_I2C_ADDR_MODE_10_BIT "


Regards

Jingyang, Teh


Jacob11's avatar
Jacob11
Icon for Occasional Contributor rankOccasional Contributor
3 years ago

I have managed to find in the i2c driver from intel (i2c_interface.c) the following code inside the i2c_read_reg function:

if (reg > 0xff) {
txbuf[0] = reg;
txbuf[1] = reg >> 8;
txsize = 2;
} else {
txbuf[0] = reg;
txsize = 1;
}

So there is at least some attempt to control the tx buffer when the value of the register is greater than 0xFF.

This TX buffer is sent to the function

alt_avalon_i2c_master_tx_rx(pdev, txbuf, txsize, rxbuf, rxsize, 0);
This function can be found in the file altera_avalon_i2c.c:
Something about this process is broken. As long as we remain in "else" everything works. As soon as
the register goes above oxFF and we need this txsize = 2 we have issues.