galileo: Add I2C callbacks example

This patch adds an example for I2C callbacks that is very similar to
the i2c-LSM9DS0 example except that it uses a PWM device that is built
into the platform.

examples/galileo/Makefile

@@ -1,6 +1,6 @@
 TARGET=galileo
 
-KNOWN_EXAMPLES = gpio-input gpio-output gpio-interrupt i2c-LSM9DS0
+KNOWN_EXAMPLES = gpio-input gpio-output gpio-interrupt i2c-LSM9DS0 i2c-callbacks
 
 ifneq ($(filter $(EXAMPLE),$(KNOWN_EXAMPLES)),)
   CONTIKI_PROJECT = $(EXAMPLE)

examples/galileo/README.md

@@ -71,6 +71,18 @@ The wiring setup is as follows (left column from Galileo and right column from L
 - SDA  and SDA
 - SCL  and SCL
 
+### I2C Callbacks (EXAMPLE=i2c-callbacks)
+
+This application is very similar to the previous one in that it also
+shows how to use I2C callback functionality, but it can be run without
+attaching any additional sensors to the platform since it simply
+communicates with a built-in PWM controller.
+
+Every five seconds, the application reads the current value of the
+MODE1 register, which should have previously been initialized to the
+value 0x20. The test verifies that this expected value is returned by
+the read.
+
 References
 ----------
 

examples/galileo/i2c-callbacks.c

@@ -0,0 +1,93 @@
+/*
+ * Copyright (C) 2015-2016, Intel Corporation. All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ *
+ * 3. Neither the name of the copyright holder nor the names of its
+ *    contributors may be used to endorse or promote products derived
+ *    from this software without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
+ * FOR A PARTICULAR PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE
+ * COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
+ * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
+ * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
+ * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
+ * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
+ * STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
+ * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED
+ * OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#include <stdio.h>
+#include <string.h>
+
+#include "contiki.h"
+#include "sys/ctimer.h"
+
+#include "i2c.h"
+
+#define PWM_PCA9685_0_I2C_ADDR 0x47
+#define MODE1_ADDR             0x00
+
+static uint8_t tx_data = MODE1_ADDR;
+static uint8_t rx_data = 0;
+static struct ctimer timer;
+
+PROCESS(i2c_callbacks_process, "I2C Callbacks Example Process");
+AUTOSTART_PROCESSES(&i2c_callbacks_process);
+/*---------------------------------------------------------------------------*/
+static void
+rx(void)
+{
+  /* The value below is programmed into this register in pwm_pca9685_init(). */
+  printf("%s expected value: %x\n",
+         (rx_data == (1 << 5)) ? "Received" : "Did not receive",
+         (unsigned)rx_data);
+}
+/*---------------------------------------------------------------------------*/
+static void
+tx(void)
+{
+  rx_data = 0;
+
+  quarkX1000_i2c_read(&rx_data, sizeof(rx_data), PWM_PCA9685_0_I2C_ADDR);
+}
+/*---------------------------------------------------------------------------*/
+static void
+err(void)
+{
+  printf("Something went wrong. err() callback has been called.\n");
+}
+/*---------------------------------------------------------------------------*/
+static void
+timeout(void *data)
+{
+  quarkX1000_i2c_write(&tx_data, sizeof(tx_data), PWM_PCA9685_0_I2C_ADDR);
+
+  ctimer_reset(&timer);
+}
+/*---------------------------------------------------------------------------*/
+PROCESS_THREAD(i2c_callbacks_process, ev, data)
+{
+  PROCESS_BEGIN();
+
+  quarkX1000_i2c_set_callbacks(rx, tx, err);
+
+  ctimer_set(&timer, CLOCK_SECOND * 5, timeout, NULL);
+
+  printf("I2C callbacks example is running\n");
+
+  PROCESS_YIELD();
+
+  PROCESS_END();
+}