Userland app for servomotor

examples/servo/Makefile

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+# Makefile for user application
+
+# Specify this directory relative to the current application.
+TOCK_USERLAND_BASE_DIR = ../..
+
+# Which files to compile.
+C_SRCS := $(wildcard *.c)
+
+# Include userland master makefile. Contains rules and flags for actually
+# building the application.
+include $(TOCK_USERLAND_BASE_DIR)/AppMakefile.mk

examples/servo/main.c

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+#include "../../libtock/interface/syscalls/servo_syscalls.h"
+#include <libtock-sync/services/alarm.h>
+#include <libtock/tock.h>
+#include <stdio.h>
+#include <stdlib.h>
+
+int main(void) {
+  // Checks if the driver exists and, if not, returns -1.
+  if (!libtock_servo_exists()) {
+    printf("There is no available servo\n");
+    return -1;
+  }
+  returncode_t result  = RETURNCODE_EOFF;
+  uint16_t servo_count = 0;
+  libtock_servo_count(&servo_count);
+  printf("The number of available servomotors is: %d", servo_count);
+  uint16_t angle = 0;
+  uint16_t index = 0; // the first index available.
+
+  if (libtock_servo_read_angle(index, &angle) == RETURNCODE_ENODEVICE) {
+    printf("\n The index number is bigger than the available servomotors\n");
+    return -1;
+  }
+
+  // Changes the angle of the servomotor from 0 to 180 degrees (waiting 0.1 ms between every change).
+  for (int i = 0; i <= 180; i++) {
+    // `result` stores the returned code received from the driver.
+    result = libtock_servo_set_angle(index, i);
+    if (result == RETURNCODE_SUCCESS) {
+      libtocksync_alarm_delay_ms(100);
+      // Verifies if the function successfully returned the current angle.
+      if (libtock_servo_read_angle(index, &angle) == RETURNCODE_SUCCESS) {
+        printf("\nThe current angle is: %d", angle);
+      }
+    } else if (result == RETURNCODE_EINVAL) {
+      printf("\nThe angle you provided exceeds 360 degrees\n");
+      return -1;
+    } else if (result == RETURNCODE_FAIL) {
+      printf("\nAngle %d exceeds the servo's limit angle.\n", i);
+    }
+  }
+  if (libtock_servo_read_angle(index, &angle) != RETURNCODE_SUCCESS) {
+    printf("\n This servo cannot return its angle.\n");
+  }
+}

libtock/interface/syscalls/servo_syscalls.c

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+#include "servo_syscalls.h"
+#include <stdio.h>
+
+bool libtock_servo_exists(void) {
+  return driver_exists(DRIVER_NUM_SERVO);
+}
+
+returncode_t libtock_servo_count(uint16_t* servo_count) {
+  uint32_t value     = 0;
+  syscall_return_t r = command(DRIVER_NUM_SERVO, 1, 0, 0);
+  // Converts the returned value stored in `r`
+  // and assigns it to `ret`.
+  returncode_t ret = tock_command_return_u32_to_returncode(r, &value);
+  *servo_count = (uint16_t)value;
+  return ret;
+
+}
+
+returncode_t libtock_servo_set_angle(uint16_t index, uint16_t angle) {
+  syscall_return_t cval = command(DRIVER_NUM_SERVO, 2, index, angle);
+  return tock_command_return_novalue_to_returncode(cval);
+}
+
+returncode_t libtock_servo_read_angle(uint16_t index, uint16_t* angle) {
+  uint32_t value     = 0;
+  syscall_return_t r = command(DRIVER_NUM_SERVO, 3, index, 0);
+  // Converts the value returned by the servo, stored in `r`
+  // and assigns it to `ret`.
+  returncode_t ret = tock_command_return_u32_to_returncode(r, &value);
+  *angle = (uint16_t)value;
+  return ret;
+}

libtock/interface/syscalls/servo_syscalls.h

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+#pragma once
+
+#include "../../tock.h"
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+#define DRIVER_NUM_SERVO 0x90009
+
+// Check if the servo system call driver is available on this board.
+bool libtock_servo_exists(void);
+// Returns the number of available servomotors.
+returncode_t libtock_servo_count(uint16_t* servo_count);
+// Change the angle.
+returncode_t libtock_servo_set_angle(uint16_t index, uint16_t angle);
+// Requests the current angle from the servo.
+returncode_t libtock_servo_read_angle(uint16_t index, uint16_t* angle);
+
+#ifdef __cplusplus
+}
+#endif