On 11/30/2013 6:39 PM, andy pugh wrote: > On 1 December 2013 00:28, Charles Steinkuehler <[email protected]> > wrote: > >> Yes, I'm pretty sure MAH is targeting the BBB. Can you provide a >> pointer or link to your arbitrary-bitfield parser? > > The parsing actually borrows code from sserial for the parsing and > processing of the bit-fields, and re-purposes much of that data > structure. > What I was hoping might stay common was the hal-file config strings. > http://www.linuxcnc.org/docs/devel/html/man/man9/hostmot2.9.html#Synchronous%20Serial%20Interface%20(SSI)
Hmm...I'm not sure there will be a lot in common with the existing hal-file strings. The modules being looked at use 16-bit digital values for acceleration in six degrees of freedom (x, y, z, plus roll, pitch, and yaw). It sort of overlaps with the encoder definitions, but not that much. The ssi_chan_N bit-field defines might be useful, but these devices are I2C and not SSI/SPI, so access is really more register oriented than bit-field. The low-level driver will probably also be polling to detect the availability of a new sample, which can happen anywhere from around once per second to about 1.3 KHz rates depending on the configuration of the sensor chip. I'll review again when I get closer to writing actual code, and feel free to suggest an appropriate mapping if you thing something makes sense. LinuxCNC doesn't really seem to have decent support for sub-buses, like I2C or even EPP, unless it's wrapped and hidden by the driver. In particular, it would be very cumbersome to write a generic I2C bus driver that could be used by various HAL components to talk to multiple different I2C target devices. Not that I'm volunteering to write this, but don't get mad at me if I implement something less than a fully generic I2C bus transport mechanism for HAL. :) ...although whatever I do will probably be at least somewhat fancier than the bit-banged I2C bus master I used for my initial LinuxCNC control tests of my 3D printer (run on an x86 system, using the software step generation thread to bit-bang I2C via 3 parallel port pins). -- Charles Steinkuehler [email protected]
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