Converting a CNC Stepper router with a handheld DSP Controller (Richauto A11)

I am using a 2nd hand CNC Router with stepper motors. Currently it is controlled by means of a handheld controller which reads the G-code programs from an USB stick (Richauto A11 DSP controller). The handheld controller is connected via a 50pin cable to a board that interfaces the controller to the stepper drivers, the VFD for the spindle and the X, Y, Z limit sensors. I would like to use LinuxCNC on this machine, replacing the handheld controller by a PC equipped with LinuxCNC, but maintaining the interface board so I can switch back to the handheld controller when necessary.
I have been able to identify the pinout of the controller and realised that the Pulse and Direction signals for the steppers are 2-wire RS422 differential signals and the rest are single-wire 5V signals.

I have been watching the Wiki and reading about the possible interfaces, but would need some initial guidance on deciding which physical interface to use, since I have no previous experience in this area (Parallel, MESA PCI-card, which MESA ?...)

Thanks in advance for any help.

Geert

replacing the handheld controller by a PC equipped with LinuxCNC, but maintaining the interface board so I can switch back to the handheld controller when necessary.

The simplest way I can think of doing it is to construct a breakout cable to go from whatever hardware you're using on LinuxCNC to plug into the RichAuto breakout box, so you can only plug one in (LCNC or the handheld controller) at any one time. However, that does assume your choice of LCNC hardware is directly compatible with the RichAuto breakout box.

I have been able to identify the pinout of the controller and realised that the Pulse and Direction signals for the steppers are 2-wire RS422 differential signals

Are you sure they're not just basic differential signals rather than RS422?

Thanks for the reply,
I was also thinking about a breakout cable, I just am not sure about which hardware to use on the LinuxCNC side. I guess that since the RichAuto board already has all the hardware (optocouplers etc...) to translate 5V signals to whatever the stepper-drivers, sensors, spindle drive etc... need, I could go for one or more parallel ports is that right ? Can I implement the differential signals on a parallel port ?

As for the differential signals, you are right, they are probably just basic differential signals, I just supposed them to be RS422 because the ICs that are on the RichAuto board are typically used as RS422 receivers.

Geert

You shouldn't need to generate differential signals if there's no reason to do so. A single-ended driver can still interface with a differential receiver; the driver signal just connects to one input of the differential receiver and the other input is grounded. As a differential receiver it is just looking for a difference between the two inputs. If both inputs are low then the output is low. If one input is high and the other low, then the output is high.

To that end, you can probably get away with just a simple parallel port setup with a basic step/dir setup per axis. You still need to do some homework to determine the correct interfacing requirements between the breakout box and the PC, but I think it should be doable.

Hi Geertd,

I apologise for bringing up an old topic!
Did you ever manage to sort this out?
I am going through a similar process and would serious love the information you got about the pin out data of the 50 pin connector from the A11 controller.
Do you still have that information that you could share with me?
Thanks,
Oakfield

Hi,

I haven't had a lot of time lately to work on this project.  I have the machine up and running and occasionally use it but right now there is no time available for further tinkering.
What I did is, I made a breakout box with two male DB25 connectors, one female DB25 connector and one 50pin connector.  The 50pin goes to the A11 controller board instead of the handheld richauto controller.  The two male DB25 connectors go to the 2 parallel ports of an old PC with LinuxCNC installed and the female DB25 connector goes to a DB25 breakout board where I connect an 8 relay board which I use to switch on the dust collector, water pump, Emergency Stop Switch and similar stuff.
Normal signals (e.g. limit switches) go directly from the A11 50pin connector to the DB25 connectors, but the stepping and direction signals go through a pair of AM26L31CN differential drivers.  S0 to S3 signals (spindle speed) require a pullup resistor.

I looked into changing the 7-Speed selection of the machine into a continuously variable speed but did not succeed.
In case you can read KiCad Files, I will attach a KiCad file with the schematic.  In case you are used to making schematics, you will probably think this is the worst schematic you ever saw... anyway it worked for me and it has helped me to make the breakout box.
In the file you will see I also tinkered with a PCB layout but never finished it.  Don't count on it, it is probably worthless.  I did the wiring by hand. 

Kind regards,

Geert