[Gregted]

I have my homebrew diy cnc machine running a code through Grblgru and am happy with it so far.

I am using a mega 2560 with ramps 1.4 board but cannot get the limit switches to work.

I have a 3d printer as well so I know how to connect X, Y, and Z limit switches to the board but the grbl wont react when I toggle the switches.

I have tried both min and max pins but no dice.

I know the switches work when I use pronterface and Marlin but would like to have them connected with grbl.

Any help appreciated.

Greg

[hfjbuis]

First is to check if the mega sees the limit switch activation

Do you have a volt meter and can you measure the voltage change on the atmega port(s) when the limit switch is activated/released!

[Gregted]

G'day and thanks for your reply,

I know the ramps board works fine with the limit switches in pronterface and marlin.

The limit switches register triggered when pressed but when I load grbl, I get no response from the motors when the switches are triggered.

I have tried the switches in both min and max on grbl but get no response.

I have just found another version of grbl for cyclone that looks promising so I'll see how that goes.

[hfjbuis]

G'day and thanks for your reply,
The limit switches register triggered when pressed but when I load grbl, I get no response from the motors when the switches are triggered.

You have to enable GRBL to response on limit switch activation. In version 1.1f set $21 to 1!

G'day and thanks for your reply,
The limit switches register triggered when pressed but when I load grbl, I get no response from the motors when the switches are triggered.

If i get it right, you use the same mega and ramps just changed firmware from marling and pronter to GRBL?

[Gregted]

Thanks again.

I have changed $21=0 to $21=1 and confirmed with $$ but still no response from steppers when I press the limit switch.

I have connected one to both min and max on the ramps board but no response from either.

I am watching the cnc the whole time so no real drama but it would be handy to have this fail safe working.

[hfjbuis]

I checked my arduino uno board, it does response to limit switch.
try the folowing:
- Disconnect limit switch
- Connect your terminal program (the one u used for setting $21=1).
- Reset atmega
you should now see the normal startup message and version information.
- connect the Limit A-axis pin on the atmega to ground.
You should see now the alarm message.

This is my message
Grbl 1.1f ['$' for help]
ALARM:1
[MSG:Reset to continue]

This is my message

You said:

I have tried both min and max pins but no dice

What do you mean by min and max pins, GRBL only has X,Y,Z limit pins!

[Gregted]

Good morning,

It's 7.30 am here in Oz so might be good evening there at 11.23 pm.

Thanks again for all your help.

I will try connecting the limit switches with the terminal window open later.

I am using Mega 2560 and ramps 1.4 board to run my cnc and it has limit pins for both min and max on all axis for 3d printer set up.

[hfjbuis]

Your ramps board has a GND and Signal pin for each Limit (X,Y,Z).
I can now reproduce your problem.
When GRBL hits a limit, all steppers are stopped immediateley. You will lose positions. GRBL will not response to any command until a reset is done.
If you then (re)boot GRBL with one of the limit switches activated, a message is send warning that the limit switch is activated, and GRBL response to commands again. This way you can jog to inactivate the limit switches.

This is the message i see when i boot GRBL having a limit switch activated:

Grbl 1.1f ['$' for help]
[MSG:Check Limits]
[MSG:'$H'|'$X' to unlock]

By default GRBL expect the limit swiches to be open when not activated (NO=Normaly Open), this way you can detect a short in the wiring. I prefer limit switches to be closed when not activated(NC=Normaly Closed) then you can detect a disconnected limit switch.
The RepRapWiki also advises to use NC

1. Connect S (top row, labelled to the left) on RAMPS to NC on the switch.
2. Connect GND on RAMPS to C on the switch

You can solve this by two ways:
- Change the wiring of you limit switches to NO
- Change the signal level of the GRBL detection by setting $5=1 (Invert Limit Pins).

My software also doesn't detect booting with the limit switch activated. I have to make a fix for this because it is important it does!

Hope this help

Huub