Primo: Problems and stuck [Updated]

Right now I basically assembled all parts of the board and the Cubetto but it looks like the wireless communication is not working.

List of Problems:

  • Cubetto did not initialize. I could hear the motors stutter but they would not move. Looks like the 4 AA batteries don’t deliver enough juice. Now I’m temporary using an old cell phone charger to deliver the power. No more wireless 😉 but it helps me troubleshooting.
    Might have to go for LiPo batteries.
  • I then tried it out with the XBees installed on the Mega and the Uno (via Wireless sd shields) respectively. But nothing happened.
    Looking at the board’s output over serial I can see that the commands are being sent. And when connecting to Cubetto using the USB cable it also initializes correctly and executes commands that I send from the laptop via serial.

So I made a step back and just wanted to setup a basic XBee connection between the two Arduinos:

I came across this tutorial from Instructables but it is not working for me.

– Mega 2560
– Arduino Wireless Protoshield SD
– XBee 2mW Wire Antenna – Series 2 (ZigBee Mesh)


void setup() {
  // initialize serial communication:

void loop(){

I have the switch on the shield on “USB” while uploading and can see “h”‘s printed in the serial window after uploading. Switching to “Micro” after that.

– Uno R3
– Arduino Wireless Protoshield SD
– XBee 2mW Wire Antenna – Series 2 (ZigBee Mesh)


int sentDat;

void setup() {
  pinMode(2, OUTPUT);

void loop() {
  if (Serial.available() > 0) {
    sentDat =;

    if(sentDat == 'h'){
      digitalWrite(2, HIGH);
      digitalWrite(2, LOW);

Again, having the switch to USB when uploading and seeing the led blink when sending an “h” over serial. Then switching to “Micro”.

And then: Nothing!

How can I troubleshoot this? Any help appreciated.


I yanked the shield from the Mega and crossed tx/rx from the Mega to the shield. I also connected the 6 isp connections plus 5v, 3.3v and GND.
I then connected Mega’s rx with Uno’s rx and tx with tx with wires and my blink sketch worked!
I had the switches on the shields both to USB.

But then, when I remove the rx/tx wires the communication is dead. I switched the shield to Micro mode and back to USB, i played around with switching rx / tx… but no luck.

Not sure if I need to make more connections from the Mega to the shield… unfortunately it’s not on


Primo: Instruction blocks and interface board

Currently working on painting the parts, glueing the interface board and putting the copper tape to it and also to the instruction blocks. To make it more difficult, the laser cut slots of the instruction blocks are slighlty narrower than the 5mm copper tape. So I need to cut off a bit from the tape so it goes through the slot. Fortunately I don’t have this problem with the too narrow slots on the interface board.

Another thing that was too small were all the holes for the 5mm LEDs on the interface board.

Can’t wait to finally start soldering!

Primo Part I: Lasering the stuff

A while ago I backed the amazing Primo project on Kickstarter. Right on schedule, the source files were available by the end of February.

Went to the local FabLab today to laser all the components.
Their lasercutter is second hand and has its hiccups. I ended up lasering all the components twice for best results. So it took me twice the time.

But I’m happy having everything at hand and start assembling. Lots of guidance is also available on Sjoerd Dirk’s Blog.