cpu/native: add qdec implementation

* Add support for the native encoder interface
* Native QDEC is there mostly for simulation
* Calling code will have to simulate QDEC increment/decrement

Signed-off-by: Gilles DOFFE <g.doffe@gmail.com>

cpu/native/include/periph_conf.h

@@ -72,6 +72,13 @@
 #endif
 /** @} */
 
+/**
+ * @brief QDEC configuration
+ */
+#ifndef QDEC_NUMOF
+#define QDEC_NUMOF (8U)
+#endif
+
 #ifdef __cplusplus
 }
 #endif

cpu/native/periph/qdec.c

+/*
+ * Copyright (C) 2017 Gilles DOFFE <gdoffe@gmail.com>
+ *
+ * This file is subject to the terms and conditions of the GNU Lesser
+ * General Public License v2.1. See the file LICENSE in the top level
+ * directory for more details.
+ */
+
+/**
+ * @ingroup     native_cpu
+ * @ingroup     drivers_periph_qdec
+ * @{
+ *
+ * @file
+ * @brief       Low-level QDEC driver implementation
+ *
+ * @author      Gilles DOFFE <gilles.doffe@gmail.com>
+ *
+ * @}
+ */
+
+#ifdef __MACH__
+#include <mach/clock.h>
+#include <mach/mach_init.h>
+#include <mach/mach_port.h>
+#include <mach/mach_host.h>
+/* Both OS X and RIOT typedef thread_t. timer.c does not use either thread_t. */
+#define thread_t riot_thread_t
+#endif
+
+#include <time.h>
+#include <sys/time.h>
+#include <signal.h>
+#include <stdint.h>
+#include <stdlib.h>
+#include <string.h>
+#include <err.h>
+#include <errno.h>
+#include <assert.h>
+
+#include "cpu.h"
+#include "cpu_conf.h"
+#include "native_internal.h"
+#include "periph/qdec.h"
+#include "periph/gpio.h"
+
+#define ENABLE_DEBUG (0)
+#include "debug.h"
+
+#ifdef QDEC_NUMOF
+
+#define NATIVE_QDEC_MAX     (0x7FFFFFFFL)
+
+/* QDEC devices */
+uint32_t qdecs[QDEC_NUMOF];
+/* QDEC values for each device, should be set externally */
+int32_t  qdecs_value[QDEC_NUMOF];
+
+int32_t qdec_init(qdec_t qdec, qdec_mode_t mode, qdec_cb_t cb, void *arg)
+{
+    /* no interrupt needed since it is externally incremented */
+    (void)cb;
+    (void)arg;
+
+    /* Verify parameters */
+    assert((qdec < QDEC_NUMOF));
+
+    /* Count on A (TI1) signal edges, B (TI2) signal edges or both,
+     * default to EINVAL (Invalid argument).
+     */
+    switch (mode) {
+        /* X1 mode */
+        case QDEC_X1:
+            break;
+        case QDEC_X2:
+        case QDEC_X4:
+        default:
+            errno = EINVAL;
+            goto err_invalid_mode;
+    }
+
+    /* Initialize qdec channels */
+    for (uint8_t i = 0; i < QDEC_NUMOF; i++) {
+        qdecs[qdec] = 0;
+    }
+
+    /* Reset counter and start qdec */
+    qdec_start(qdec);
+
+    return 0;
+
+/* Error management */
+err_invalid_mode:
+    return errno;
+}
+
+/* Return QDEC value */
+inline int32_t qdec_read_and_reset(qdec_t qdec)
+{
+    int32_t count = 0;
+
+    count = qdecs_value[qdec];
+    qdecs_value[qdec] = 0;
+
+    return count;
+}
+
+/* Return QDEC value */
+inline int32_t qdec_read(qdec_t qdec)
+{
+    return qdecs_value[qdec];
+}
+
+/* Empty functions to keep API */
+void qdec_start(qdec_t qdec)
+{
+    (void)qdec;
+}
+
+void qdec_stop(qdec_t qdec)
+{
+    (void)qdec;
+}
+
+#endif /* QDEC_NUMOF */