I'm trying to figure out why my X-axis is moving in the wrong direction. Nothing I do seems to invert the direction. Which lead me to some general questions about the configuration of GRBL for GRBLShield.
If I read the TI data sheet correctly,
$3 should be "2", the number of uSec per step pulse.
$7 should be 0bxxx111, since the step pulses for the TI 8811 are active high, while GRBL assumes that all signals are active low.
Is that right?
(BTW, I wasn't able to find the GRBL forum to post questions. Do you have a link?)
This sounds like a hardware problem to me. If the direction line for the X axis is not working correctly then the axis will only move in one direction. Do you have the ability to see if the dir signal is being set correctly? I know this is a bunch of work involving an oscilloscope and probes, and may be too much. Depends on your time, equipment and skills. Alternately we can send out another board if you will return yours.
As for grbl SW support, the place to look is the grbl github. The Issues tab has a pretty active forum with Sonny Jeon (Chamnit) handling the lion's share opf the requests. github.com/grbl/grbl
Sorry, wasn't clear: The X-axis will move in both directions, but the movement is reversed, i.e., g0x10 cuts to the left, g0x-10 cuts to the right. That's what I need to change, and thus my questions about setting up grbl's configuration variables.
I can check it out on the scope, plenty of htem here in the lab. :-}
Yes, this is the invert mask. It's a bit confusing. You can use the invert mask to change the direction in software. I have to refer you to the grbl documentation on how to use this setting. https://github.com/grbl/grbl/wiki/Configuring-Grbl
I do believe you are correct. I've never had to mess with the grbl default settings other than setting the motor steps, $0, $1, $2. Grblshield should be just plug and play.
$3 is the step pulse width. The stepper drivers on grblshield can take as little as 1 microsecond, but I'm not sure what the lower range if grbl is. 2 should work.
$7 is the invert mask. It should work with standard grbl settings - try $7=0. Note that bits 0 and 1 are not used, so the bitmask actually looks like: 0b Zdir Ydir Xdir Zstep Ystep Xstep 0 0
Try this and see if it works. If the motors turn the wrong direction you have to add 32 to the number to invert the X direction, 64 to the number to invert Y and 128 to invert Z - i.e. $7=32 to invert X, $7=96 to invert both X and Y, etc.
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