G'Day Guy's,
           Well with the GUI Controls now available on HDMI with my recent coding for the Surface Grinder Project when I started thinking about this new project the fact we have 4 axis to play with I do have a few spare 3 jaw chucks so a new A axis project is going to happen and just ordered a stepper motor and DM556 micro stepper for the project.

Now on my Surface Grinder Project Lyle suggested a 1K/22k with a BC337 translator to the DIR/STEP outputs so does this give full isolation to the pico pins ?

With the new board to be made for the breakout board to my CNC I will have a go at doing a schematic first so it can go past the brains trust before committing to design the board.

Regards Bryan

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Bryan, I suggest you use opto-isolators, get familiar with the concept of current transfer ratio, CTR. Even I understand this. BC337's give no isolation, and just short-circuit all their pins together if they fail.

Well Lyle has been helping me along and has suggested using 2 pico's, now where a 2350A chip is just a few dollars this PICO 3 Computer is much more expensive.

While I was waiting for my daughters this morning got thinking about this, so if we set the 2350A on my stepper board to USB so it can accept CDC input/output then it would be easy to transmit the G-code line by line via the USB. So the big question with hte PICO 3 USB Hub can it be used for this purpose.

Now being able to scan a part and save it to a file where the area is defined then the Y axis is set at the end of each pass to move y$ The X axis stepped slowly until the microswitch is closed then the Z axis it moved higher and the microswitch constantly tested for when it opens.

So each X movement on completion can broadcast it to the PICO 3 where it can be saved to a file or with some coding drawn on the monitor so one can verify the scan.

My soldering iron handpiece should be here soon so I can get the V2 stepper board made and then the surface grinder project can be completed.

Regards Bryan

G'day,
I have been working on this in the background and have made a few false starts at getting it running.

Unfortunately life and figuring out how to make a living keeps getting in the way, not to mention about 1000000 other half baked ideas running around the grey matter  

So the basic idea is to have 2 controllers, one a CNC controller on the machine, and one as a G-Code transmitter / HMI:

Use a standard PICO2 at the CNC machine end as a stand alone controller running the STEPPER SYSTEM under MMBasic, this:
Accepts G-Code and Outputs STEP/DIR/EN to the Stepper Drivers.
Monitors the Homing / Limit / Stop switches and transmits status and position.

The G-Code transmitter end can be pretty much anything, but a PICOMITE HDMIUSB or a PC make the most sense:
Runs a simple MMBasic / Python program to parse and send G-Code to the CNC controller.
Accepts return strings / position information / status from the CNC controller.

If we use a standard PICO2 at the CNC end we have the option of using the USB-CDC to communicate with the G-Code transmitter or using a USB-TTL232 converter, this gives us as an example:

GP00-GP01 USB-TTL
GP02-GP03 I2C RTC + OLED status display? + Extra I/O via expanders
GP04-GP06 X Axis EN/STP/DIR
GP07-GP09 Y Axis EN/STP/DIR
GP10-GP12 Z Axis EN/STP/DIR
GP13-GP15 A Axis EN/STP/DIR
GP16-GP21 X-X,Y-Y,Z-Z Limits
GP22      E-Stop
GP26-GP28 AUX Analog / Encoder / Limits / Spindle

OR:

GP00-GP01 USB-TTL
GP02-GP03 I2C RTC + OLED status display? + Extra I/O via expanders
GP04      SPINDLE
GP05      ENABLE
GP06-GP07 X Axis STP/DIR
GP08-GP09 Y Axis STP/DIR
GP10-GP11 Z Axis STP/DIR
GP12-GP13 A Axis STP/DIR
GP14-GP15 Spare
GP16      E-Stop
GP17-GP19 X,Y,Z Limits
GP20-GP28 AUX Analog / Encoder / Limits

For more I/O use an RP2350B instead, although 22 I/O from the PICO2 should be enough for most systems.

The advantage of using the USB-TTL converter is we can opto-isolate the USB system and thus protect the G-Code transmitter from any spikes etc, this is my current plan after seeing several PC motherboards and LPT cards damaged by spikes on what where supposed to be isolated systems, I think it is much better to destroy an $11AUD PICO2 than anything more expensive.

Also means we only need one PICO COMPUTER3 / PC / Monitor for all the different machines.

This is still a work in motion so any ideas welcome.

Regards, Lyle.

Lyle as I did make the V2 CNC board we may aswell use that and as we are using it as a slave no LCD will be needed which does leave the 12 pin LCD connector free to use.

I have an old USB-TTL converter in a drawer that has sat there for over a decade which I can use and GP8, GP9 are brought out to a header too.

I am slowly getting my head around this probe for scanning parts which could also be a good tool for debugging etc as the USB-TTL connection can be fine tuned using this method.

Now as we are receiving data from the V2 CNC board a good idea would be to draw it on the screen then that bit of code can be used for normal operation where when making a part it is drawn on the screen.

Yes a heap of grey matter is going to be used to work this out as reading that python book is bringing back memories from a very long time ago.

Regards Bryan