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!
-Stefan
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
values (SERIAL_CLOCK, BIDIRECTIONAL_DATA, SET_CLOCK_SRC,
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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