Trying to understand how the DDK works

Question

Hi,
1.)  If I wanted to be able to use a wide variety of NI DAQ cards
under the QNX RTOS, would the NI Measurement Hardware DDK be able to
faciliate this?
2.)  From looking at the web-page describing the DDK, it looks to
me that the driver code written by NI is done in a platform indepedant
way, using only ANSI C/C++ function, and when it needs
to do something platform specific, it calls out to functions that I can
provide.  Is this correct?  I am envisioning having to
provide code to get PCI resources, attach to interrupt, hw I/O.... am I
on the right track?
3.)  I've downloaded the NI HW DDK OTHER code, but it's not clear to me
how the platform-dependant code for QNX will integrate with this.  I
have the DAQ PCI_E_series Register Level Programming Manual
and STC manual, but I can't find any docs on how to use the code in
this archive.  What am I missing?
Thanks

Answer 1

Hi,
1.)  If I wanted to be able to use a wide variety of NI DAQ cards
under the QNX RTOS, would the NI Measurement Hardware DDK be able to
faciliate this?
Depends.  MHDDK provides register information for a number of NI
DAQ devices.  There isn't an API that abstracts the measurement
task form the hardware, like DAQmx does.
You would need to write the high level functions for each type of
device you what to use and provide an API to your application that
would select the appropriate device specific function.  I guess
something like
startDevice()
    // somehow get deviceTypeId
    switch (deviceTypeId)
    case kMSeries:
          mseries_startDevice();
    case ESeries
          eseries_startDevice();
or using function pointers, or c++ inheritance.  There are many possibilities...
2.) .... am I
on the right track?
Yes.  MHDDK only abstracts device access using the iBus and
tAddressSpace objects.  The iBus contains the address spaces of
the device.  You request address spaces from the bus and use it
write/read from the device.  For PCI devices the read/write
functions using pointer manipuilation.  For a PCMCIA device on a
x86 you would use the port io instructions.
iBus objects are created and destroy using the factory methods
acquireBoard() and releaseBoard().  This is where all the platform
dependent magic should occur.  Here are a couple of KBs with more info:
Measurement Hardware Driver Development Kit Register Level Programming Architecture
How to Make an iBus
3.)  I've downloaded the NI HW DDK OTHER code, but it's not clear to me
how the platform-dependant code for QNX will integrate with this.  I
have the DAQ PCI_E_series Register Level Programming Manual
and STC manual, but I can't find any docs on how to use the code in
this archive.  What am I missing?
In  osiUserCode.cpp, implement acquireBoard(tChar*) and
releaseBoard(iBus *&).   To acquire the board you usually
have to loacte the device, find bar0 and bar1 , and map them to the
current address space. 
This article shows exactly how to do that in QNX: Talking to hardware under QNX Neutrino
Also, create a QNX specific structure to
attach to the iBus where you can store any handles you need for
releaseBoard() to clean up.
Hope this helps.
Diego