Finally, test if our setup is correct. Also if you want to get rid completely of your device — try to unload DT overlay along with driver. I tried to understand it all, but I guess my knowledge about coding is rather limited. A way to add it to the existing driver through the means of an “overlay”. The two functions that do all the heavy lifting are the “readReg ” and “writeReg ” functions.

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The second link will also help you determine if you have a rev1 or rev2 board if you do not already know. The instructions are as follows: This might be the source of your problem: The two functions that do all the heavy lifting lijux the “readReg ” and “writeReg ” functions.

Also if you want to get rid completely of your device — try to unload DT overlay along with driver. This little document explains how this is done. I also found the following link to be very helpful. The A2,A1,A0 pins are all connected to ground meaning that our 7-bit device address is really 0b or 0x The DT snippet from below can be used to register the kernel driver with pull-ups enabled on all pins and single IRQ connected to gpio 23 from the SoC.

CONFIG_GPIO_MCP23S08: Microchip MCP23xxx I/O expander

Then, my code will pool all MCP’s to find out which port has changed – This should be much more efficient than pooling all MCP’s every second or so My experiences so far with the MCP and the GPIO Linux driver shown that the interrupt handling does not exist, and I guess that is what is been discussed here: If this is the right device overlay how do I load it to the driver?


The patch to fix the pinctrl driver that was mentioned by the other poster is in the 4. Personally I didn’t try any of those, so you should look which works for you best. My feeling is you will be much better of with your original approach.

Lines beginning with ” ” are ignored. But on the main subject, the problem I see is that the gpio interrupt signal is being handled by the bcmpinctrl driver, which does not know that the mcp driver is supposed to handle it.

MCP23017 IO Expansion

I was able to use this to change the I2C bus speed to KHz. Could not set address to 0x I reviewed the bcm pinctrl driver and the pcm driver. Did you use lsmod to verify the driver was loaded? Make sure that the A2, A1 and A0 pins are all grounded, making the the 7-bit device address of the MCP “” in binary which is equivalent of 0x20 hex.

Jörg Faschingbauer – MCP IO Expansion

Because I don’t own the other 3 ICs, I would like to invite owners of one or more of the following to get in contact with me, so we can test them Apparently you don’t have your device MCP described in Mco23017 Tree, that’s why probe is not called. These resistors are already on the Raspberry Pi so there’s no need to provide them ourselves.


No mainstream GPIO expansion possible, as we saw. Finally, test if our setup is correct. Matching happens when compatible field of your driver found in Device Tree for your driver it’s “microchip,mcp” string.

Faschingbauer und Schaar JavaScript free Generated by nanoc. So either the device tree file for your board should have this description, or you should create your mvp23017 device tree overlay for your device and load it along with driver.

Both are detected at addresses 0x20 and 0x I found none, so I wrote my own Currently it only supports the MCP, as it is the only one I mcp230117 available here to test it.

For those interested, I will post it here: Please note that a mcp2017 kernel is needed for this. Basically both constructors set the i2C device name, device address and then call the “openI2C ” method which in turn calls the “open ” system call to open the I2C device in question and return a file descriptor saved in the private variable “i2cDescriptor”. Check the logs what they say; I once had the case the driver could not detect the chip at startup, for example.

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