function that returns the number of servomotors available

Author: inesmaria08

examples/servo/main.c

@@ -11,9 +11,13 @@ int main(void) {
     return -1;
   }
   returncode_t result = RETURNCODE_EOFF;
+  uint16_t servo_number = 0;
+  libtock_servo_number(&servo_number);
+  printf("The number of available servomotors is: %d", servo_number);
   uint16_t angle = 0;
   uint16_t index = 0; // the first index available.
 
+
   if (libtock_current_servo_angle(index, &angle) == RETURNCODE_ENODEVICE) {
     printf("\n The index number is bigger than the available servomotors\n");
     return -1;

libtock/interface/syscalls/servo_syscalls.c

@@ -5,15 +5,26 @@ bool libtock_servo_exists(void) {
   return driver_exists(DRIVER_NUM_SERVO);
 }
 
+returncode_t libtock_servo_number(uint16_t* servo_number){
+  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_number = (uint16_t)value;
+  return ret;
+
+}
+
 returncode_t libtock_servo_angle(uint16_t index, uint16_t angle) {
-  syscall_return_t cval = command(DRIVER_NUM_SERVO, 1, index, angle);
+  syscall_return_t cval = command(DRIVER_NUM_SERVO, 2, index, angle);
   return tock_command_return_novalue_to_returncode(cval);
 }
 
 returncode_t libtock_current_servo_angle(uint16_t index, uint16_t* angle) {
   uint32_t value     = 0;
-  syscall_return_t r = command(DRIVER_NUM_SERVO, 2, index, 0);
-  // Converts the value returned by the servo, stored in `r`,
+  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;

libtock/interface/syscalls/servo_syscalls.h

@@ -10,7 +10,8 @@ extern "C" {
 
 // 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_number(uint16_t* servo_number);
 // Change the angle.
 returncode_t libtock_servo_angle(uint16_t index, uint16_t angle );
 // Requests the current angle from the servo.