Access to device connected RaspBerryPi SPI bus from IOC-Client

[Christian Pauly <pauly@physik.uni-wuppertal.de>]

Dear folks
I am trying to provide EPICS support for a magnetic field Hall sensor 
which is connected to a RaspberryPi via SPI bus.
I want to run an EPICS-IOC on this same Raspberry, which provides the 
data from the Hall-Sensor on request, such that some CSS-Gui, running on 
another pc, can access the sensor-data via Channel Access.

I have a running EPICS base on the Raspberry, and i know how to readout 
the sensor in a small c++ program (using the wiringPiSPI library).


What is the best way now, to get the sensor-data into the EPICS IOC ?

My first idea is, to modify the c++-program such, that it prints the
return-value as a formatted text string.
Then there might be an EPICS record-type, which can call this programm 
(via SHELL-command), capture the text output, evaluate the outputstring, 
and copy this into the record data field.

However, that does not sound like an elegant solution. So what is the 
suggested solution, and does anyone maybe have an example of a similar 
implementation ?

I have a basic EPICS knowledge, i know what a record is, and i can 
configure a database with different records.
But i have no idea how to program eg a new record type by using some 
EPICS libraries.


Can anyone help ?????
Or give me a hint where i can find appropriate documentation ?


Best regards,
Christian