Add second example, tweak example1 overlay

jimbojr · jimbojr · commit 375bb14c75e2 · 2015-06-03T14:32:29.000+01:00
diff --git a/hardware/computemodule/cm-peri-sw-guide.md b/hardware/computemodule/cm-peri-sw-guide.md
@@ -148,9 +148,9 @@ You can include more diagnostics in the output by adding `dtdebug=1` to `config.
 
 Please use the [Device Tree subforum](https://www.raspberrypi.org/forums/viewforum.php?f=107) on the Raspberry Pi forums to ask Device Tree related questions.
 
-##Worked Examples
+##Examples
 
-For these simple worked examples I used a CMIO board with peripherals attached via jumper wires.
+For these simple examples I used a CMIO board with peripherals attached via jumper wires.
 
 For each of the examples we assume a CM+CMIO board with a clean install of the latest Raspbian version on the CM. See instructions [here](https://www.raspberrypi.org/documentation/hardware/computemodule/cm-emmc-flashing.md).
 
@@ -162,7 +162,7 @@ If you suspect any issues or bugs with Device Tree it is always best to try a `s
 
 Please post any issues / bugs / questions on the Raspberry Pi [Device Tree subforum](https://www.raspberrypi.org/forums/viewforum.php?f=107).
 
-##Worked Example 1 - attaching an I2C RTC
+##Example 1 - attaching an I2C RTC
 
 In this simple example we wire an NXP PCF8523 real time clock (RTC) to the CMIO board GPIO pins (3V3, GND, I2C1_SDA on GPIO44 and I2C1_SCL on GPIO45).
 
@@ -212,7 +212,41 @@ sudo hwclock
 
 will return with the hardware clock time, and not an error.
 
-##Worked Example 2 - Attaching an ENC28J60 SPI Ethernet Controller
+##Example 2 - Attaching an ENC28J60 SPI Ethernet Controller
 
-Coming soon...
+In this example we take the first RTC example and add another peripheral - an ENC28J60 SPI Ethernet Controller. The Ethernet controller is connected to SPI pins CE0, MISO, MOSI and SCLK (GPIO8-11 respectively), as well as GPIO12 for a falling edge interrupt, and of course GND and 3V3.
 
+In this example we won't change `dt-blob.bin` (though of course you can if you wish) and we should see that Linux Device Tree correctly sets up the pins.
+
+Grab [example2-overlay.dts](example2-overlay.dts) and put it in `/boot` then compile it:
+```
+sudo dtc -@ -I dts -O dtb -o /boot/overlays/example2-overlay.dtb /boot/example2-overlay.dts
+```
+
+Edit `/boot/config.txt` and add the line:
+```
+dtoverlay=example2
+```
+
+Now save and reboot.
+
+Once rebooted you should see, as before, an rtc0 entry in /dev and running:
+```
+sudo hwclock
+```
+
+will return with the hardware clock time, and not an error.
+
+You should also have Ethernet connectivity:
+```
+ping 8.8.8.8
+```
+
+should work.
+
+finally running:
+```
+sudo raspi-gpio get
+```
+
+should show that GPIO8-11 have changed to ALT0 (SPI) functions.
diff --git a/hardware/computemodule/example1-overlay.dts b/hardware/computemodule/example1-overlay.dts
@@ -16,37 +16,33 @@
         brcm,pins = <44 45>;
         brcm,function = <6>; /* alt2 */
       };
+      spi0_pins: spi0_pins {
+        brcm,pins = <7 8 9 10 11>;
+        brcm,function = <4>; /* alt0 */
+      };
     };
   };
 
   //
-  // I2C at 100KHz
+  // I2C Device(s)
   //
   fragment@1 {
     target = <&i2c1>;
     __overlay__ {
+      #address-cells = <1>; /* needed to avoid dtc warning */
+      #size-cells = <0>; /* needed to avoid dtc warning */
       pinctrl-names = "default";
       pinctrl-0 = <&i2c1_pins>;
       clock-frequency = <100000>;
-    };
-  };
-
-  //
-  // Add devices to I2C1 Bus:
-  //  PCF8523 RTC device
-  //
-  fragment@2 {
-    target = <&i2c1>;
-    __overlay__ {
-      #address-cells = <1>;
-      #size-cells = <0>;
       status = "okay";
-      pcf8523@68 {
+      // PCF8523 RTC device
+      pcf8523@68 { 
         compatible = "nxp,pcf8523";
         reg = <0x68>;
         status = "okay";
       };
     };
   };
 
+
 };
diff --git a/hardware/computemodule/example2-overlay.dts b/hardware/computemodule/example2-overlay.dts
@@ -0,0 +1,80 @@
+// Example overlay for PCF8523 RTC device + ENC28J60 Ethernet
+/dts-v1/;
+/plugin/;
+
+/ {
+  compatible = "brcm,bcm2708";
+
+  //
+  // Set up GPIOs:
+  //  I2C1 on GPIO44,45
+  //  SPI on GPIO8-11
+  //  ENC28J60 interrupt on GPIO12
+  //
+  fragment@0 {
+    target = <&gpio>;
+    __overlay__ {
+      i2c1_pins: i2c1 {
+        brcm,pins = <44 45>;
+        brcm,function = <6>; /* alt2 */
+      };
+      spi0_pins: spi0_pins {
+        brcm,pins = <8 9 10 11>;
+        brcm,function = <4>; /* alt0 */
+      };
+      // ENC28J60 Ethernet Interrupt GPIO
+      eth1_pins: eth1_pins {
+        brcm,pins = <12>;
+        brcm,function = <0>; /* in */
+        brcm,pull = <0>; /* none */
+      };
+    };
+  };
+
+  //
+  // I2C Device(s)
+  //
+  fragment@1 {
+    target = <&i2c1>;
+    __overlay__ {
+      #address-cells = <1>; /* needed to avoid dtc warning */
+      #size-cells = <0>; /* needed to avoid dtc warning */
+      pinctrl-names = "default";
+      pinctrl-0 = <&i2c1_pins>;
+      clock-frequency = <100000>;
+      status = "okay";
+      // PCF8523 RTC device
+      pcf8523@68 { 
+        compatible = "nxp,pcf8523";
+        reg = <0x68>;
+        status = "okay";
+      };
+    };
+  };
+
+  //
+  // SPI Device(s)
+  //
+  fragment@2 {
+    target = <&spi0>;
+    __overlay__ {
+      #address-cells = <1>; /* needed to avoid dtc warning */
+      #size-cells = <0>; /* needed to avoid dtc warning */
+      pinctrl-names = "default";
+      pinctrl-0 = <&spi0_pins>;
+      status = "okay";
+      // ENC28J60 SPI Device
+      eth1: enc28j60@0{
+        compatible = "microchip,enc28j60";
+        reg = <0>; /* CE0 */
+        pinctrl-names = "default";
+        pinctrl-0 = <&eth1_pins>;
+        interrupt-parent = <&gpio>;
+        interrupts = <12 0x2>; /* falling edge */
+        spi-max-frequency = <12000000>;
+        status = "okay";
+      };
+    };
+  };
+
+};
