Custom GPIO driver for nct5104d

GPIO driver for nct5104d with PCEngines APU board support. This driver has been build by the need of customised home automation approach.

I would like to make one big and important notice here this is my first driver on linux so it might be that some approaches could have been done better - contribution welcome :)

Driver exposes registry access for shared devices configuration registries as well as GPIO control. Driver is created with only GPIO management hence it is by default using

logical device id 0x07 

Driver

I originally have build the driver to run on Centos machines. Therefore the master branch does contain the most recent build for that. If there are any other compilations then they should be listed as '<DistroName>_<kernel-ver>' in the branch tree i.e.

CentOs_3.10.0-514.16.1.el7.x86_64

Compiling driver

Start by checking out the source code ( if you are using centos you should be good to pull master )

git clone git@github.com:RafPe/gpio-driver-nct5104d.git

Navigate to the directory

cd gpio-driver-nct5104d

Run make file

make 

Once completed you should be just able to stream it with the use of insmod

insmod nct5104d_gpio.ko

If everything went fine you will see your driver in the lodaded modules

>  lsmod | grep nct5104d_gpio
Module                  Size  Used by
nct5104d_gpio          13230  0

Examing the dmesg to check device initialised properly

> dmesg | grep nct5104d_gpio:
[  363.782812] nct5104d_gpio: Initialiazing device ...
[  363.787826] nct5104d_gpio: Registered correctly with major number 248
[  363.800784] nct5104d_gpio: Succesfuly registered char device
[  363.809339] nct5104d_gpio: Found device with chip ID (APU)  : 0xc452
[  363.815803] nct5104d_gpio: Succesfuly registered platform device

You should also see device under the /dev space

> ls -l /dev/nct*
crw-------. 1 root root 248, 0 Apr 29 18:07 /dev/nct5104d_gpio

Debugging

If for whatever reason something would not be working as expected you can compile driver with debug mode enabled.

For that you need to uncomment define in nct5104d_gpio.h file

/*--------  uncomment below to enable debugging  --------*/

//#define DRIVER_DEBUG

Then in dmesg you will have much more output based on interactions you try with the driver.

Pin management - nct5104dpin

I have made the life bit easier by providng binary app for pin management called nct5104dpin. In order to use it navigate to nct5104dpin folder and execute the following:

make 
make install

which should compile and install the application under the /usr/local/bin/nct5104dpin

Examples of pin management

nct5104dpin [ --get|--set ] [--pin ] --val < 0|1 > --dir <direction_for_gpio>

Get a pin value: nct5104dpin --pin 7 
Get a pin value: nct5104dpin --get --pin 14
Set a pin value: nct5104dpin --set --pin 14 --val 1
Set a pin direction: nct5104dpin --set --pin 14 --dir out

Return data example

nct5104dpin --pin 1 | jq
[
  {
    "pin": 1,
    "value": 0
  }
]

Bulk modification of pin status

This is possible however with use of registry management. You can directly write desired values to specific rgistries using nct5104dreg app

Registry management - nct5104dreg

I have made the life bit easier by providng binary app for pin management called nct5104dreg. In order to use it navigate to nct5104dreg folder and execute the following:

make 
make install

which should compile and install the application under the /usr/local/bin/nct5104dreg

Examples of registry management

nct5104dreg [ --get|--set ] [--reg ] <HEX> --val <DECIMAL> 

Get a reg value: nct5104dreg --reg 0x07 
Get a reg value: nct5104dreg --get --reg 0x07
Set a reg value: nct5104dreg --set --reg 0xE0 --val 252

Return data example

nct5104dreg --reg 0xE1 | jq
[
  {
    "registry": "0xe1",
    "value": 248
  }
]

References

• Originally based and inspired by https://github.com/tasanakorn/linux-gpio-nct5104d