Step 6: Prepare the Arduino.

For the Arduino I started out writing my own software. But while searching for a good way to control movement from the serial port I stumbled upon something called "Grbl ". This is a g-code interpreter with lots of nifty functions. As I already had everything connected to the Arduino I had to ether change my connections or change the software. Luckily it is easy to change control pins in the software. I did however have to download Winavr and then the code from github.com . It is not that hard to do. After downloading and extracting the code you have to change the port numbers in config.h and make sure you get them in the right order. Then all you have to do is start a command window, enter the correct folder and type "make". If all goes to plan you should end up with a .hex file ready for the Arduino.

I have however changed the pin-out since then and here in the instructable I use the default pin-out of Grbl. This will make it a lot simpler to follow and setup. You can just download the prepared hex file from the Grbl download page .

The current version of Grbl (0.6b) has a bug in the queue system. The laser on and off (M3, M5) commands are not put in the queue and the laser will be turned on and off as soon as the Arduino receives the commands. This is resolved in the edge branch. You can download and the source from here , or grab the compiled hex I am using from here . This should resolve the issue until the next version of Grbl.

Any way you choose to do it you will end up with a .hex file that you must get into the Arduino. I have tried a couple of different ways and the one I like the most is by a program called XLoader . The programming is pretty straight forward; select the correct serial port for your Arduino. Select the hex file and type of Arduino and press upload. If you are using the new Arduino Uno the XLoader doesn’t work, you will get an upload error. In that case I recommend using ARP/Arduino Uploader but even this uploader has some issues with the Uno. When programming the Arduino select the com port and microcontroller in the respective dropdown. After that you will have to make a change in the “AVR Dude Params” text. Erase the “-b19200” (without the quotes) part and click on the upload button. In any case, a couple of seconds later you are done and are ready to try it out. Exit the XLoader and get to the next paragraph.

The Arduino needs to be set up for the job. Start your favorite serial terminal and open the port your Arduino is connected to. You should get a welcome message:

Grbl 0.6b
'$' to dump current settings"

If you enter $ followed by return you will get a list of options. Something like this:

$0 = 400.0 (steps/mm x)
$1 = 400.0 (steps/mm y)
$2 = 400.0 (steps/mm z)
$3 = 30 (microseconds step pulse)
$4 = 480.0 (mm/sec default feed rate)
$5 = 480.0 (mm/sec default seek rate)
$6 = 0.100 (mm/arc segment)
$7 = 0 (step port invert mask. binary = 0)
$8 = 25 (acceleration in mm/sec^2)
$9 = 300 (max instant cornering speed change in delta mm/min)
'$x=value' to set parameter or just '$' to dump current settings

You must change the steps/mm for X and Y axis to 53.333 on both. Just enter "$0=53.33" followed by return and then "$1=53.333" followed by return. Z axis can be ignored as it is not used. The acceleration can be ramped up to something like 100 ("$8=100" and return). As we move really slowly with this machine acceleration can be high. Another side effect of low acceleration can be that curves get a lot more burnt than straight lines as the controller constantly tries to accelerate and decelerate but never reach full speed. If you build this like me one of your axis might be mirrored. This is easy to fix. Option $7 lets you change direction on axis. I wanted to change direction on the X axis so I type in "$7=8" as I want to change bit 3 (8 = 00001000 binary) if you want to change direction on Y axis you type in 16 (00010000) or 24 (00011000) to change both. The complete documentation of the invert mask can be found here .

Now you are ready for the computer setup. If you want to try some movement you can type "G91 G28 X0 Y0 [return]" to zero the axis. Followed by "X10 Y10 [enter]". You should see 10mm movement on each of the axis.

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Bio: I'm just a poor lonesome cowboy... Not really, I am divorced and live in the cold country of Sweden. I am not much of ... More »
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