{"id":1134,"date":"2017-07-14T15:49:16","date_gmt":"2017-07-14T14:49:16","guid":{"rendered":"http:\/\/ofalcao.pt\/blog\/?p=1134"},"modified":"2017-07-26T14:38:10","modified_gmt":"2017-07-26T13:38:10","slug":"codatex-rfid-sensor","status":"publish","type":"post","link":"https:\/\/ofalcao.pt\/blog\/2017\/codatex-rfid-sensor","title":{"rendered":"Codatex RFID Sensor"},"content":{"rendered":"

Some time ago, when I started to use RFID tags with an automated LEGO train<\/a>, I found out that there was a RFID sensor available for the MINDSTORMS NXT, the Codatex RFID Sensor for NXT<\/a>:<\/p>\n

<\/p>\n

Codatex doesn’t make them aymore so I ordered one from BrickLink but never got it working with ev3dev. I put it on the shelf hoping that after a while, with ev3dev constant evolution, things would get better.<\/p>\n

Last month Michael Brandl told me that the Codatex sensors were in fact LEGO sensors and he asked if it was possible to use with EV3.<\/p>\n

Well, it is possible, just not with original LEGO firmware. At least LeJOS<\/a> and RobotC<\/a> have support for the Codatex RFID Sensor. But not ev3dev \ud83d\ude41<\/p>\n

So this holidays I put the Codatex sensor on my case, decided to give it another try.<\/p>\n

I read the documentation from Codatex and the source code from LeJOS and RobotC and after a while I was reading the sensor properties directly from shell.<\/p>\n

After connecting the sensor to Input Port 1 I need to set the port mode to “other-i2C”:<\/p>\n

echo other-i2c > \/sys\/class\/lego-port\/port0\/mode<\/pre>\n
Currently there are two I2C modes in ev3dev: “nxt-i2c” for known NXT devices and “other-i2c” for other I2C devices, preventing the system to poll the I2C bus.<\/p>\n
To read all the Codatex registers this line is enough:<\/p>\n
\/usr\/sbin\/i2cset -y 3 0x02 0x00 ; \/usr\/sbin\/i2cset -y 3 0x02 0x41 0x83; sleep 0.1; \/usr\/sbin\/i2cdump -y 3 0x02<\/pre>\n
(first wake up the sensor with a dummy write, then initialize the firmware, wait a bit and read everything)<\/p>\n
Error: Write failed\r\nNo size specified (using byte-data access)\r\n 0 1 2 3 4 5 6 7 8 9 a b c d e f 0123456789abcdef\r\n00: 56 31 2e 30 00 00 00 00 43 4f 44 41 54 45 58 00 V1.0....CODATEX.\r\n10: 52 46 49 44 00 00 00 00 00 00 00 00 00 00 00 00 RFID............\r\n20: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................\r\n30: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................\r\n40: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................\r\n50: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................\r\n60: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................\r\n70: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................\r\n80: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................\r\n90: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................\r\na0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................\r\nb0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................\r\nc0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................\r\nd0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................\r\ne0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................\r\nf0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................<\/pre>\n
The “Error: Write failed” is expected because the dummy write that wakes the Codatex sensor fails.<\/p>\n
I got excited, it seemed easy.<\/p>\n
So to read just once (singleshot mode) this should work:<\/p>\n
\/usr\/sbin\/i2cset -y 3 0x02 0x00 ; \/usr\/sbin\/i2cset -y 3 0x02 0x41 0x01; sleep 0.25; \/usr\/sbin\/i2cdump -r 0x42-0x46 -y 3 0x0<\/pre>\n
(wake up, send a singleshot read command, wait for aquiring, read the 5 Tag ID registers)<\/p>\n
But it didn’t work:<\/p>\n
Error: Write failed\r\nNo size specified (using byte-data access)\r\n 0 1 2 3 4 5 6 7 8 9 a b c d e f 0123456789abcdef\r\n40: 00 00 00 00 00 .....<\/pre>\n
The next days I read lots of code from the web, even from\u00a0Daniele Benedettelli old NXC library<\/a>. It seemed that my timings were wrong but I could not understand why.<\/p>\n
After asking for help at ev3dev<\/a> I found the reason: the Codatex sensor needs power at pin 1 for the RFID part. So the I2C works but without 9V at pin 1 all readings will fail.<\/p>\n
LeJOS and RobotC activate power on pin1 but the two ev3dev I2C modes don’t do that. ITo be sure I tried LeJOS and finally I could read my tags:<\/p>\n
package PackageCodatex;\r\n\r\nimport lejos.hardware.Brick;\r\nimport lejos.hardware.port.SensorPort;\r\nimport lejos.hardware.sensor.RFIDSensor;\r\n\r\npublic class Codatex\r\n{\r\n    public static void main(String[] args)\r\n    {\r\n    \tRFIDSensor rfid = new RFIDSensor(SensorPort.S1);\r\n\t\tSystem.out.println(rfid.getProductID());\r\n\t\tSystem.out.println(rfid.getVendorID());\r\n\t\tSystem.out.println(rfid.getVersion());\r\n\t\ttry {Thread.sleep(2000);}\r\n\t\tcatch (InterruptedException e) {}\r\n\t\tlong transID = rfid.readTransponderAsLong(true);    \r\n\t\tSystem.out.println(transID);\r\n\t\ttry {Thread.sleep(5000);}\r\n\t\tcatch (InterruptedException e) {}\r\n\t}\r\n}<\/code><\/pre>\n
David Lechner gave some hint on how to write a driver but honestly I don’t understand at least half of it. So I made a ghetto adapter with a MINDSTORMS EV3 cable and a 9V PP3 battery and it finally works – I can read the Codatex 4102 tags as well as my other 4001 tags:<\/p>\n