{"id":1069,"date":"2017-04-17T15:48:30","date_gmt":"2017-04-17T14:48:30","guid":{"rendered":"http:\/\/ofalcao.pt\/blog\/?p=1069"},"modified":"2017-04-18T20:09:37","modified_gmt":"2017-04-18T19:09:37","slug":"using-grove-devices-to-the-ev3","status":"publish","type":"post","link":"https:\/\/ofalcao.pt\/blog\/2017\/using-grove-devices-to-the-ev3","title":{"rendered":"Using Grove devices to the EV3"},"content":{"rendered":"

After David Lechner announced ev3dev support for it I’ve been planning to offer myself a couple of BrickPi 3 from Dexter Industries<\/a> (just one is not enough since the BrickPi 3 suports daisy chaining).<\/p>\n

While I wait for european distributors to sell it (and my budget to stabilize) and since I’m also playing with magnets, I ordered a mindsensors.com Grove adapter<\/a> so I can start testing Grove devices with my Ev3. Also got two Grove devices from Seeed Studio at my local robotics store, will start with the easiest one: Grove – Electromagnet<\/a>.<\/p>\n

ev3dev doesn’t have a Grove driver yet but since the adapter is an I2C device it recognizes it and configures it as an I2C host:<\/p>\n

[\u00a0 563.590748] lego-port port0: Added new device 'in1:nxt-i2c-host'\r\n[\u00a0 563.795525] i2c-legoev3 i2c-legoev3.3: registered on input port 1<\/pre>\n
Addressing the Grove adpter is easy, just need to follow the ev3dev documentation (Appendix C : I2C devices<\/a>):<\/p>\n
robot@ev3dev:~$ ls \/dev\/i2c-in*\r\n\/dev\/i2c-in1\r\n\r\nrobot@ev3dev:~$ udevadm info -q path -n \/dev\/i2c-in1\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 \u00a0\r\n\/devices\/platform\/legoev3-ports\/lego-port\/port0\/i2c-legoev3.3\/i2c-3\/i2c-dev\/i2c-3<\/pre>\n
So the Grove adapter is at I2C bus #3. According to mindsensors.com User Guide<\/a>, it’s address is 0x42. That’t the unshifted address but fot i2c-tools we need to use the shifted address (0x21 – at the end of the ev3dev Appendix C doc there is a table with both addresses).<\/p>\n
robot@ev3dev:~$ sudo i2cdump 3 0x21\r\n\r\n\u00a0\u00a0\u00a0\u00a0 0\u00a0 1\u00a0 2\u00a0 3\u00a0 4\u00a0 5\u00a0 6\u00a0 7\u00a0 8\u00a0 9\u00a0 a\u00a0 b\u00a0 c\u00a0 d\u00a0 e\u00a0 f\u00a0\u00a0\u00a0 0123456789abcdef\r\n00: 56 31 2e 30 32 00 00 00 6d 6e 64 73 6e 73 72 73\u00a0\u00a0\u00a0 V1.02...mndsnsrs\r\n10: 47 61 64 70 74 6f 72 00 00 00 00 00 00 00 00 00\u00a0\u00a0\u00a0 Gadptor.........\r\n20: 4a 61 6e 20 30 34 20 32 30 31 35 00 31 32 46 31\u00a0\u00a0\u00a0 Jan 04 2015.12F1\r\n30: 38 34 30 00 00 00 00 00 00 00 00 00 00 00 00 00\u00a0\u00a0\u00a0 840.............\r\n40: 00 97 03 32 00 00 00 00 00 00 00 00 00 00 00 00\u00a0\u00a0\u00a0 .??2............\r\n50: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00\u00a0\u00a0\u00a0 ................\r\n60: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00\u00a0\u00a0\u00a0 ................\r\n70: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00\u00a0\u00a0\u00a0 ................\r\n80: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00\u00a0\u00a0\u00a0 ................\r\n90: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00\u00a0\u00a0\u00a0 ................\r\na0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00\u00a0\u00a0\u00a0 ................\r\nb0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00\u00a0\u00a0\u00a0 ................\r\nc0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00\u00a0\u00a0\u00a0 ................\r\nd0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00\u00a0\u00a0\u00a0 ................\r\ne0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00\u00a0\u00a0\u00a0 ................\r\nf0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00\u00a0\u00a0\u00a0 ................<\/pre>\n
Acording to the User Guide, this is the expected content of the first 24 registers:<\/p>\n
0x00-0x07: Software version \u2013 Vx.nn
\n0x08-0x0f: Vendor Id – mndsnsrs
\n0x10-0x17: Device ID \u2013 Gadptor<\/p>\n
So I have a v1.02 Grove adapter.<\/p>\n
To use the Grove – Electromagnet I just need to send a “T” (0x54) to the Command Register (0x41) to set the Grove Adapter into “Transmit” mode and next set the Operation Mode, which can be “Digital_0” (sending 0x02 to the Operation Mode register at 0x42) or “Digital_1” (sending 0x03 to the Operation Mode register).<\/p>\n
So to turn the electromagnet ON:<\/p>\n
sudo i2cset -y 3 0x21 0x41 0x54\r\nsudo i2cset -y 3 0x21 0x42 0x03<\/pre>\n
And to turn it OFF:<\/p>\n
sudo i2cset -y 3 0x21 0x41 0x54\r\nsudo i2cset -y 3 0x21 0x42 0x02<\/pre>\n