Hi Alexis,

  thanks  a lot for all these suggestions. For my applications, the functions 
you listed below would be entirely sufficient. Essentially, I need to be able 
to put selected channels on the DIO in either read or write mode, and then 
simply read from them or write from them. The protocol I use requires 16 data 
bits, and 3 additional control lines. It was originally implemented under 
vxWorks. Nothing fancy at all.

Thanks a lot for your kind help!


On Dec 21, 2009, at 15:23, Alexis Berlemont wrote:

> Hi,
> Stefan Schaal wrote:
>> Hi everybody,
>> we have an NI6259 board working xenomai 2.5, using the analogy APIs.
>> Read/write to analog channels is quite straightforward and can be
>> inferred from the cmd_read and cmd_write source code. Now I would also
>> like to use the digital I/O of this board (e.g., the 32 digital I/O
>> lines). In Comedi, there are functions to set the DIO lines to
>> input/output mode (comedi_dio_config), and then functions to read/write,
>> like comedi_dio_read and comedi_dio_write. Does xenomai/analogy already
>> have similar functionality?
> Many thanks for this question, it is an issue I have been
> keeping on postponing the resolution. Currently, the functions are not 
> implemented but it could be quickly done.
> Here is my understanding of the Comedi DIO features; please, correct
> me if I am wrong.
> In Comedi, here is the list of functions related with DIO:
> - comedi_dio_read (insn_read or deprecated insn trigger)
> - comedi_dio_write (insn_write or deprecated insn trigger)
> - comedi_dio_config (insn_config or deprecated insn trigger)
> - comedi_dio_get_config (insn_config or deprecated trigger)
> - comedi_dio_bitfield (insn_bits or comedi_dio_read/write)
> - comedi_dio_bitfield2 (insn_bits or comedi_dio_read/write)
> The instruction insn_bits is a combination of a read operation and a
> write operation (that is why, the function comedi_dio_bitfield* call
> comedi_dio_read and comedi_dio_write if the driver does not provide an
> insn-bits handler).
> I had a look at many Comedi drivers and most of them register the
> handler "insn_bits" for the DIO subdevice. The instructions insn_read
> and insn_write are not oftenly used in DIO contexts.
> comedi_dio_bitfield() uses the insn_bits instruction. However, it only
> works with DIO subdevice limited to 32 channels; that was why
> comedi_dio_bitfield2() was introduced, this latter function contains
> one more argument so as to shift the bits.
> Consequently, we may need a more limited set of functions:
> - a4l_sync_dio(dsc, idx_subd, mask, buf)
> - a4l_sizeof_subd(dsc, idx_subd)
> - a4l_config_subd(dsc, idx_subd, idx_chan, cfg_type, *val)
> a4l_sync_dio() could work with any DIO subdevice (more or less than 32
> channels). The last argument would be a pointer to a buffer which size
> should be defined thanks to a4l_sizeof_subd() (8, 16, 32, 64 or more
> bits).
> a4l_config_subd() could be used to configure the polarity of the DIO
> channels. The argument cfg_type could be set to DIO_INPUT, DIO_OUTPUT,
> DIO_QUERY. And, we could even imagine that this function would not be
> limited to DIO subdevice; so, the argument cfg_type could accept more
> GET_CLOCK_SRC, etc.)
> How do you see this approach ?
> Do you (or anyone else) have a better solution in mind ?
> Best regards,
>> Thanks a lot,
>> -Stefan
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> Alexis.

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