{"id":817,"date":"2014-11-21T07:41:29","date_gmt":"2014-11-21T07:41:29","guid":{"rendered":"http:\/\/ofalcao.pt\/blog\/?p=817"},"modified":"2016-06-14T15:30:45","modified_gmt":"2016-06-14T14:30:45","slug":"lego-wedo-with-linux","status":"publish","type":"post","link":"https:\/\/ofalcao.pt\/blog\/2014\/lego-wedo-with-linux","title":{"rendered":"LEGO WeDO with Linux"},"content":{"rendered":"

After almost 2 years of procrastination I finally offered myself a LEGO WeDO USB Hub<\/a>:<\/p>\n

\"\"<\/a><\/p>\n

I just love the WeDO idea: with just a small and somewhat simple interface (the USB Hub) anyone can use a PC (nowadays a\u00a0ubiquitous appliance) to control a motor or read a sensor. Great for educational uses, specially with STEM (Science, Technology, Engineering and Mathematics).<\/p>\n

Sadly the LEGO WeDO family got much less attention than his older and bigger related, LEGO Mindstorms<\/a> (at least in my country, Portugal). Although a bit less expensive than an NXT or an EV3, it’s not cheap so the EV3 seems a better investment (more pieces, more diversity, more power).<\/p>\n

Early this year I used a Raspberry Pi with a Piface Digital board<\/a> as a clumsy but much more powerful DIY alternative to the WeDO. This was in fact the trigger to start using LEGO again, event registering myself in a LUG<\/a>.<\/p>\n

This week someone opened an issue with ev3dev asking for “Any chance of adding Lego WeDo hub + motor and sensors?<\/a>“. Right after I suggested wedo<\/a> (a python library for WeDO) Ralph Hempel<\/a> announced he was working in linux kernel support for WeDO (not just for ev3dev, could be used with other systems… like my laptop). Wow!<\/p>\n

So I got a pair of WeDO USB hubs and a tilt sensor<\/a>. And while waiting for Ralph’s work, I’m using WeDo with a variant of the wedo library: WeDoMore<\/a>.<\/p>\n

This is what you need to get WeDoMore working with Linux (both Ubuntu 14.10 and ev3dev tested, no need to use sudo in ev3dev because I’m already root): first download it <\/a>and extract it, then:<\/p>\n

sudo apt-get install python-pip\r\nsudo pip install pyusb\r\ncd WeDoMore-master\r\nsudo .\/setup.py install<\/pre>\n
With Ubuntu it was necessary to remove Ubuntu’s version of pyusb, much older than pypi version:<\/p>\n
sudo apt-get remove pyusb<\/pre>\n
Now connect the WeDO USB Hub and check with ‘dmesg’ and ‘lsusb’.<\/p>\n
On Ubuntu:<\/p>\n
413.597110] usb 2-1.3: new low-speed USB device number 10 using ehci-pci\r\n[\u00a0 413.695628] usb 2-1.3: New USB device found, idVendor=0694, idProduct=0003\r\n[\u00a0 413.695639] usb 2-1.3: New USB device strings: Mfr=0, Product=2, SerialNumber=0\r\n[\u00a0 413.695644] usb 2-1.3: Product: LEGO USB Hub V1.00\r\n[\u00a0 413.700722] hid-generic 0003:0694:0003.0009: hiddev0,hidraw3: USB HID v1.10 Device [LEGO USB Hub V1.00] on usb-0000:00:1d.0-1.3\/input0<\/pre>\n
Bus 002 Device 013: ID 0694:0003 Lego Group<\/pre>\n
On ev3dev:<\/p>\n
[ 1263.539342] usb 1-1.2: new low-speed USB device number 4 using ohci\r\n[ 1263.698363] hid-generic 0003:0694:0003.0001: device has no listeners, quitting<\/pre>\n
Bus 001 Device 004: ID 0694:0003 Lego Group<\/pre>\n
So Ubuntu has a better knowledge of the WeDO USB Hub than ev3dev, don’t know why.<\/p>\n
Now let’s test it from the python shell:<\/p>\n
~$ python\r\nPython 2.7.8 (default, Oct 20 2014, 15:05:19)\r\n[GCC 4.9.1] on linux2\r\nType \"help\", \"copyright\", \"credits\" or \"license\" for more information.\r\n>>> from wedo import WeDo\r\n>>> wd = WeDo()\r\n>>> wd.motor_a=100<\/pre>\n
If you have a motor connected to port A, it shell spin (note that as WeDO gets it power from USB the motor will get only 5V instead of ~9V as with Power Functions batteries… so it will spin slower).<\/p>\n
To stop the motor and leave the shell:<\/p>\n
>>> wd.motor_a=0\r\n>>> exit()<\/pre>\n
As I also have a tilt sensor I made this simple control script:<\/p>\n
#!\/usr\/bin\/env python\r\n\r\nfrom wedo import WeDo\r\nfrom time import sleep\r\n\r\nwd = WeDo()\r\nprint(\"Tilt me!\")\r\nwhile(True):\r\n\u00a0if(wd.tilt==2): \r\n\u00a0\u00a0 wd.motor_a=35\r\n\u00a0elif(wd.tilt==3):\r\n\u00a0\u00a0 wd.motor_a=-35\r\n\u00a0else:\r\n\u00a0\u00a0 wd.motor_a=0<\/pre>\n