So I started to search if there is already some overlay existing for these chips. Any idea what is the problem here? Finally, we have a variable for storing the device address which in our case we know is 0x You can try to load your overlay like described in that article: Board index All times are UTC. The next two parameters represent the register address and the data to be written into that register address. The Raspberry is a good and well-maintained and well-documented platform, and MCP is a popular and cheap port expander, so it makes sense to use that combination for the following walk-through.

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Any help would be appreciated. Or you can try to use Capemgr for this purpose. Writing as “out” defaults to initializing the value as low.

Possibly you could use one of those chips and just copy their code. By using our site, you acknowledge that you have read and understand our Cookie PolicyPrivacy Policyand our Terms of Service.

linux – MCP I2C Device driver probe function is not called – Stack Overflow

The preconfigured user pi already is; see here for more. For those interested, I will post it here: I haven’t tried it myself to do with the chip. The data is then shifted out of the slave and into the master.

The A2,A1,A0 pins are all connected to ground meaning that our 7-bit device address is really 0b or 0x So I started to search if there is already some overlay existing for these chips. So either the device tree file for your board should have this description, or you should create your own device tree overlay for your device and load it along with driver. Decoding much of the code for the “readReg ” and “writeReg ” functions was the toughest part for me.


It doesn’t let you set the value of a pin before making it an output and it only lets you deal with one pin at a time which makes it even slower than it needs to be going through the kernel will always be a slow way of doing GPIO but having to do it one bit at a time multiplies the overheadI would expect performance to be even worse in the case of an IO expander.

Your overlay looks fine, it doesn’t appear to be anything missing: The chip’s power pins are connected to the power rails. There is one interrupt registered. Post Your Answer Discard By clicking “Post Your Answer”, you acknowledge that you have read our updated terms of serviceprivacy policy and cookie policyand that your continued use of the website is subject to these policies.

Next we will see how to automatically load and parameterize that driver.

The second link will also help you determine if you have a rev1 or rev2 board if you do not already know. Post as a guest Name. Stack Overflow works best with JavaScript enabled. Test the Wiring Given that we correctly wired the I2C pins, we should now see someone there on the bus at address 0x I highly recommend that you download the i2c-tools package using the following command: This little document explains how this is done.


But when I try the i2cdetect command it shows UU.

CONFIG_GPIO_MCP23S08: Microchip MCP23xxx I/O expander

Insert as root, obviously the i2c-dev kernel module. The data received from the I2C device is then read into the “data” variable via the “inbuff” pointer.

With a rmmod mcp command I see the device still under devices but i2cdetect shows 0x20 So you unloaded the driver and now i2cdetect shows you that there is some device on 0x20 address. The MCP has a 7-bit device address. The bootloader combines these together with the basic blob, and passes the resulting hardware description to the kernel.

But it didnt work. By using it, porting your code is as easy as changing a few pin numbers. I reviewed the bcm pinctrl driver and the pcm driver. Also if you want to get rid completely of your device — try to unload DT overlay along with driver.

As for your questions, — I’ll try to address them a bit later. I would like to check it.