Category Archives: Stuff

Test GUI for Grbl without Arduino using the Simulator and virtual com port under GNU Linux.

My Arduino is not accabale right now but I wanted to look at a new GUI or gcode sender program for Grbl called SourceRabbit GCode Sender. I already had the simulator compiled and ready to go and the next step was just to find a way to connect both together. I found that the program socat can do just this:

socat -d -d pty,raw,echo=0,link=/tmp/ttyV0 pty,raw,echo=0,link=/tmp/ttyV1

This creates two virtual serial ports with the names /tmp/ttyV0 and /tmp/ttyV1 and connect both together. Now I just need to direct the output and input of Grbl to one of the virtual serial ports:

./grbl_sim -n > /tmp/ttyV0 < /tmp/ttyV0

To test if this works I can use a command line terminal program like miniterm and connect to the other virtual serial port /tmp/ttyV1

Now that everything is working I can finally test the new SourceRabbit GCode Sender program.

chrubuntu: zram-config is working wonders if ram runs out… no more freezing desktop.

I’m using chrubuntu on a acer 710 since a long time and it works well, but sometime I ran out of ram and the PC freezes, this happens a lot with Chrome if I open multiple tabs. I was just looking for ways to limit Chrome ram uses but stumbled on the zram stuff and it looks like this helps. I was able to open 15 tabs with different pages and no crash.

sudo apt-get install zram-config

That’s it.

Linux image to laser g code converter


I did find imagecarve a GPL V2 open source program. After mapping the Z axis to S spindle values it looks like the g code it spits out could work with my laser. I only did test this with the greate grbl simulator, but I would guess after some more tweaking it should work on the real machine too.

Here is my Github project with the source files.

IMG_20140920_121713Looks like the image gets flipped when burned, but I flipped it back for this page. I think cardboard in not the best medium for laser engravings, it burns too fast.

real time spindle control aka laser mode for grbl

G20 G90 G64 G40
T0 M6
G1 F500

G0 X0 Y0 Z0
G1 X20

G0 X0 Y5 Z0
G1 X10
G1 X20

G0 X0 Y10 Z0
M3 S64
G1 X10
G1 X20

G0 X0 Y20 Z0
G1 X10 S255
G1 X20 S127
M5 s0

G0 X0 Y25 Z0
G1 X5 S128
G1 X10 S300
G1 X15 S1000
G1 X20 S255


Here are the changes:
Github Link

Compile time option example:
#if defined(LASER_SPINDLE) && defined(USE_LINE_NUMBERS)
void plan_buffer_line(float *target, float feed_rate, uint8_t invert_feed_rate, float rpm, uint8_t direction, int32_t line_number);
#elif defined(LASER_SPINDLE)
void plan_buffer_line(float *target, float feed_rate, uint8_t invert_feed_rate, float rpm, uint8_t direction);
#elif defined(USE_LINE_NUMBERS)
void plan_buffer_line(float *target, float feed_rate, uint8_t invert_feed_rate, int32_t line_number);
void plan_buffer_line(float *target, float feed_rate, uint8_t invert_feed_rate);

Grbl 0.9g settings for my Shapeoko


>>> $$
$0=10 (step pulse, usec)
$1=25 (step idle delay, msec)
$2=0 (step port invert mask:00000000)
$3=2 (dir port invert mask:00000010)
$4=0 (step enable invert, bool)
$5=0 (limit pins invert, bool)
$6=0 (probe pin invert, bool)
$10=3 (status report mask:00000011)
$11=0.050 (junction deviation, mm)
$12=0.002 (arc tolerance, mm)
$13=0 (report inches, bool)
$14=1 (auto start, bool)
$20=1 (soft limits, bool)
$21=0 (hard limits, bool)
$22=1 (homing cycle, bool)
$23=1 (homing dir invert mask:00000001)
$24=25.000 (homing feed, mm/min)
$25=250.000 (homing seek, mm/min)
$26=250 (homing debounce, msec)
$27=3.000 (homing pull-off, mm)
$100=87.489 (x, step/mm)
$101=87.489 (y, step/mm)
$102=640.000 (z, step/mm)
$110=4000.000 (x max rate, mm/min)
$111=4000.000 (y max rate, mm/min)
$112=650.000 (z max rate, mm/min)
$120=15.000 (x accel, mm/sec^2)
$121=15.000 (y accel, mm/sec^2)
$122=15.000 (z accel, mm/sec^2)
$130=204.000 (x max travel, mm)
$131=204.000 (y max travel, mm)
$132=54.000 (z max travel, mm)

DD WRT OPENVPN setup for Firmware: DD-WRT v24-sp2 (03/25/13) mega

This is how I configured OPEN VPN on my DD WRT router:

All the key generation tutorials are still good, but with the new firmware most of the settings are now in GUI:

Internal local IP range:
VPN IP range

DNS extra settings:


push "route"
push "dhcp-option DNS"
push "comp-lzo no"

fire wall rules:

iptables -I INPUT 1 -p udp --dport 1194 -j ACCEPT
iptables -I FORWARD 1 --source -j ACCEPT
iptables -I FORWARD -i br0 -o tun2 -j ACCEPT
iptables -I FORWARD -i tun2 -o br0 -j ACCEPT
iptables -t nat -A POSTROUTING -s -j MASQUERADE

Client File, like client1.ovpn:

remote 1194
remote-cert-tls server
dev tun0
proto udp
resolv-retry infinite

SECRET blablabla

SECRET blablabla

SECRET blablabla