EBC Exercise 12 I2C - Revision history

Yoder: Added Intro to i2c and SPI link

2013-06-05T15:21:46Z

Added Intro to i2c and SPI link

2013-05-31T19:58:58Z

‎From the Shell

2013-05-29T18:17:24Z

2013-05-29T18:16:22Z

‎The Hardware

2013-05-29T17:56:55Z

Updated for 3.8

2013-03-02T09:41:03Z

‎bone

2013-03-02T09:19:45Z

‎From the Shell

2013-03-02T09:17:33Z

‎bone

2012-09-12T21:53:48Z

‎References

2012-09-05T02:03:11Z

‎From C

@@ Line 140: / Line 140: @@
 == References ==
 # [http://www.microchip.com/wwwproducts/Devices.aspx?dDocName=en010749 TC74] I2C Temperature Sensor information.
 # I got a lot information from [[Interfacing with I2C Devices]].

@@ Line 71: / Line 71: @@
 The Beagle brings out I²C bus 2 (bus 3 on the bone) to the Expansion Header. You can see what devices are on the bus by using the [http://www.lm-sensors.org/wiki/man/i2cdetect i2cdetect] command. On your Beagle try:
-  beagle$ '''i2cdetect -y -r 3'''  (use '''-r 2''' on the xM)
+  beagle$ '''i2cdetect -y -r 1'''
   1  2  3  4  5  6  7  8  9  a  b  c  d  e  f
 :          -- -- -- -- -- -- -- -- -- -- -- -- --

@@ Line 21: / Line 21: @@
 You can see what's on the i2c buses with
   beagle$ '''i2cdetect -y -r 0'''
   beagle$ '''i2cdetect -y -r 1'''
   1  2  3  4  5  6  7  8  9  a  b  c  d  e  f
@@ Line 31: / Line 40: @@
 : -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
 : 70 -- -- -- -- -- -- --
-I have something at addresses 0x48, 0x4f and 0x70.
+I have something at addresses 0x48, 0x4f and 0x70 on bus 1.
 [[File:HeaderP9.jpg|.jpg|800px]]

@@ Line 7: / Line 7: @@
 == The Hardware ==
 === bone ===
 The AM3359 on the BeagleBone has three I²C controllers (Section 21 of the [http://www.ti.com/product/am3359 TRM]). You can see which ones are configured at boot time by running the following on the Beagle:
   beagle$ '''dmesg | grep i2c'''
-  [    0.102508]  omap_i2c.1: alias fck already exists
+  [    0.153495] omap_i2c 44e0b000.i2c: bus 0 rev0.11 at 400 kHz
-  [    0.116668] omap_i2c omap_i2c.1: bus 1 rev2.4.0 at 100 kHz
+  [    0.165269] omap_i2c 44e0b000.i2c: unable to select pin group
-  [    0.241516]  omap_i2c.3: alias fck already exists
+  [    0.166036] omap_i2c 4819c000.i2c: bus 1 rev0.11 at 100 kHz
-  [    0.241790] omap_i2c omap_i2c.3: bus 3 rev2.4.0 at 100 kHz
+  [    0.168388] omap_i2c 4819c000.i2c: unable to select pin group
-  [    0.532775] i2c /dev entries driver
+  [    0.418600] i2c /dev entries driver
-Here we see two buses, running at the same speed. Table 11 from the SRM shows buses 1 and 2 are brought out to the P9 Expansion Header, however remember the table starts numbering with 0 and the software starts with 1, so these are really buses 2 and 3.  We'll use 3 since 2 isn't configured.
+You can see what's on the i2c buses with
-[[File:Bone P9 pinout.jpg|400px]]
+[[File:HeaderP9.jpg|.jpg|800px]]
 These signals are 3.3V and the TC74 runs on 2.7 to 5.5V so we are in luck.

@@ Line 2: / Line 2: @@
 [[Category:EmbeddedBeagleClass]]
 {{YoderHead}}
 [http://en.wikipedia.org/wiki/I%C2%B2C I²C] is a "two-wire interface" standard that is used to attach low-speed peripherals to an embedded system.  In this exercise we will wire up a couple of I²C temperature sensors ([http://www.microchip.com/wwwproducts/Devices.aspx?dDocName=en010749 TC74]) and learn how to read their values.

@@ Line 82: / Line 82: @@
 : -- -- -- -- -- -- -- --
-What you see is a list of all the devices found on the bus. I've attached three TC74's, a TC74A0, a TC74A2 and a TC74A3.  Their address are <code>1001 000</code>, <code>1001 010</code> and <code>1001 011</code> respectively.  Converting to hex you get <code>0x48</code>, <code>0x4a</code> and <code>0x4b</code>.  You can see the two appear in the ic2detect.
+What you see is a list of all the devices found on the bus. I've attached three TC74's, a TC74A0, a TC74A2 and a TC74A3.  Their address are <code>1001 000</code>, <code>1001 010</code> and <code>1001 011</code> respectively.  Converting to hex you get <code>0x48</code>, <code>0x4a</code> and <code>0x4b</code>.  You can see the three appear in the ic2detect.
 Each TC74 has two registers.

@@ Line 119: / Line 119: @@
 Compile and run '''myi2cget.c'''.
-  beagle$ '''gcc myi2cget -o myi2cget'''
+  beagle$ '''gcc myi2cget.c -o myi2cget'''
   beagle$ '''./myi2cget'''
   Usage:  ./myi2cget <i2c-bus> <i2c-address> <register>