On Tue, 25 Feb 2014, Jeff wrote:
Date: Tue, 25 Feb 2014 10:37:38 -0800
From: Jeff <xylo...@hotmail.com>
Reply-To: "Enhanced Machine Controller (EMC)"
<emc-users@lists.sourceforge.net>
To: "Enhanced Machine Controller (EMC)" <emc-users@lists.sourceforge.net>
Subject: Re: [Emc-users] beaglebone fpga with linuxcnc
Hi,
Some info about the FPGA boards on my site: At this point, the FPGA boards
I have listed don't have any released software support to go with them. I'm
going to work on making a library for simple I/O. This version of the board
uses the same BBB I/O pins that Charles's MachineKit uses for STEP/DIR, etc.
as I had read negative comments on the internet about using the BBB's eMMC
data path. Thus the data/control to the FPGA is currently done with
"bit-bang" type control. To mask all of that I'll simply have a library
with 4 basic functions: SelectRead and SelectWrite which set an address and
do a byte read or write. Then there would be the ReadMore and WriteMore
type functions which get/set the next byte using auto increment feature
built in to FPGA firmware. I have all of this tested and working so far.
These are used to have a psuedo simulation of a PC EPP parallel port. This
basically means address register read/write and data register read/write,
with auto increment on the data register R/W using 8 data bits, and 4
control lines (ASTROBE, DSTROBE RD_WRn and RDY).
I've also written a small program that will take a Xilinx BIN file and
dump it to the FPGA to program that device. The software manipulates the
bytes individually so no "bit swapping" is necessary. This version of board
does not read any data stream out of the FPGA it simply dumps the firmware
data to the FPGA and waits for the DONE to be properly set. Programing of
the FPGA firmware using the BBB is very quick (much faster than my parallel
port JTAG progamming port).
At first I attempted to configure the setup with Hostmot2 and hm2_7i43
software. After a bit I was able to get both hostmot2 and hm2_7i43 working
on the BBB side. Then I started looking in to the FPGA side and had to back
off (whoa!). While I was able to get that whole suite to compile for the X9
part I couldn't run it properly. I think that there are some differences
that might need changing, for example the X9 does not use the DCM like the
Spartan3 series does (though it interestingly enough compiled). There may
be some other dialects between parts that need a bit of code modification as
well; I was seeing warning about how RAM blocks were being used.
The 7I43 FPGA code should run fine in a Spartan6, but note that because of the
way the driver does the startup sequence and the VHDLs dependence on its
helper CPLD, its not likely to work as-is
The 7i90 branch VHDL source (TopEPPSHostMot2) is designed to work with a
pre-configured FPGA with no helper CPLD (the 7I43 has a helper CPLD to allow
USB bootstrap). TopEPPSHostMot2 source code is more suited for Spartan6 , and
should allow the use of MesaFlash utility to program both user and fallback
FPGA configurations into an attached SPI flash chip.
As mentioned, I decided to back off, so what I did next was to modify the
PPMC code. I've written a simple VHDL program to generate the encoders and
PWM registers to do some simple tests. Using Hostmot/7i43 might be a final
solution, but I'm still learning the way LinuxCNC (and Linux in general)
works. Anyway, right now I'm adapting the PPMC software to work with a small
I/O board I made. As can be seen on my web pages, the FPGA board has two
50-pin IDC headers, each with 24 pins of I/O from the FPGA. These signals
are routed through FET bus switches, which are enabled with the MachineKit
BB_IO_RDY# signal. All FPGA I/O must be 3.3V logic (no 5V at all). Each
signal has a GND pin associated with it (pin 1-signal, pin 2-GND, and so on,
with pin 49 being 3V3 and pin 50 again GND). I've made a mating I/O board
that uses one of these ports. The I/O board routes a FPGA signal past a
diode from GND to signal,and from signal to 3.3V, then through a 47 ohm
resistor to be used on-board. The I/O board has 4 encoder set ports
(singled ended A, B, I, 5V and GND on each of the four) which are RC
buffered and logic level shifted through LVC541 buffers. It also has four
discrete inputs set per axis (16 total discrete inputs on four 6-pin
headers). It also has 4 outputs ports (Signal A, Signal B and an ENA#
signal, along with 5V and GND). The Signal A and B could be used for
STEP/DIR or PWM/DIR. The ENA# is common to all four ports. These outputs
are driven by LVC06, open collector buffers to the 5 pin headers (5V S1, S2,
ENA#, GND). I also have a single 10 pin header with 8 discrete output
signals on it also buffered through LVC06's. 7 main outputs lines, and the
same ENA# that is used on the other outputs. The discrete I/O are sent SPI
fashion from the FPGA to the I/O board which has a XC2C64A CPLD to do
translation. This allowed my to have all of the I/O and still only use the
24 pins available on one port of the FPGA board. Anyone who's interest can
see a quick photo of the I/O board mentioned here:
http://xylotex.netfirms.com/OSCommerce/catalog/product_info.php?cPath=27&products_id=64
I hope to have the I/O board and firmware on the FPGA board talking with
the modified PPMC software some time before the daylight savings time kicks
in.
Jeff
----------------------------------------
Date: Tue, 25 Feb 2014 07:45:42 -0600
From: josiahmor...@gmail.com
To: emc-users@lists.sourceforge.net
Subject: [Emc-users] beaglebone fpga with linuxcnc
I noticed that xylotex has an fpga cape in the works for beaglebone black.
(as well as other similar items from other sources)
I was curious if anyone was looking into the implementation of such fpga
capes into a linuxcnc build.
also, what would be the benefits and drawbacks to the addition of this fpga
module?
has anyone thought about how linuxcnc would be able to actually take
advantage of the fpga capabilities?
I'm just curious because I could see some benefits of possibly allowing the
fpga to house the kinematics functions as well as drive multiple step pins
simultaneously. I just don't know how linuxcnc would command it.
anyway, I just wanted to bring this up for discussion and see what thoughts
people had on it.
thanks.
--
Josiah Morgan, P.E.
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