Servo library tested and debugged.

Some additional HardwareTimer methods introduced to make this
convenient; ancillary libmaple/timers.h changes resulted.

3 files changed, 289 insertions, 0 deletions

diff --git a/libraries/Servo/Servo.cpp b/libraries/Servo/Servo.cpp
new file mode 100644
index 0000000..4f60fbe
--- /dev/null
+++ b/libraries/Servo/Servo.cpp
@@ -0,0 +1,138 @@
+/******************************************************************************
+ * The MIT License
+ *
+ * Copyright (c) 2010, LeafLabs, LLC.
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+ * THE SOFTWARE.
+ *****************************************************************************/
+
+#include "boards.h"
+#include "io.h"
+#include "pwm.h"
+#include "wirish_math.h"
+
+#include "Servo.h"
+
+// Configure prescaler and overflow for a 20msec period (could just
+// use HardwareTimer::setPeriod(), but this lets conversions below
+// happen more statically, in combination with an inlined map() -- a
+// premature optimization? TODO profile speed/size tradeoff)
+#define CYC_20MSEC     (20000 * CYCLES_PER_MICROSECOND)
+#define SERVO_PRE ((uint16)((CYC_20MSEC >> 16) + 1))
+#define SERVO_OVF ((uint16)((CYC_20MSEC / SERVO_PRE) - 1))
+#define SERVO_TAU_USEC \
+    ((uint32)(((double)SERVO_OVF) * SERVO_PRE / CYCLES_PER_MICROSECOND + 0.5))
+
+#define US_TO_COMPARE(us) ((uint16)map(us, 0, SERVO_TAU_USEC, 0, SERVO_OVF))
+#define COMPARE_TO_US(c)  ((uint32)map(c, 0, SERVO_OVF, 0, SERVO_TAU_USEC))
+
+#define ANGLE_TO_US(a)  ((uint16)(map(a, 0, 180, this->min, this->max)))
+#define US_TO_ANGLE(us) ((uint8)(map(us, this->min, this->max, 0, 180)))
+
+Servo::Servo() {
+    this->pin = NOT_ATTACHED;
+    this->timer = 0;
+    this->channel = TIMER_INVALID;
+    this->min = SERVO_DEFAULT_MIN_PW;
+    this->max = SERVO_DEFAULT_MAX_PW;
+}
+
+bool Servo::attach(uint8_t pin) {
+    return this->attach(pin, SERVO_DEFAULT_MIN_PW, SERVO_DEFAULT_MAX_PW);
+}
+
+bool Servo::attach(uint8_t pin, uint16_t min, uint16_t max) {
+    timer_dev_num timer_num = PIN_MAP[pin].timer_num;
+    uint32_t channel = PIN_MAP[pin].timer_chan;
+    if (timer_num == TIMER_INVALID) {
+        // don't reset any members or ASSERT(0), to keep driving any
+        // previously attach()ed servo.
+        return false;
+    }
+    this->pin = pin;
+    this->timer = getTimer(timer_num);
+    this->channel = channel;
+    this->min = min;
+    this->max = max;
+
+    pinMode(pin, PWM);
+
+    this->timer->pause();
+    this->timer->setPrescaleFactor(SERVO_PRE);
+    this->timer->setOverflow(SERVO_OVF);
+    this->timer->generateUpdate();
+    this->timer->resume();
+    return true;
+}
+
+bool Servo::detach() {
+    if (this->pin == NOT_ATTACHED) return false;
+
+    this->timer->setChannelMode(this->channel, TIMER_DISABLED);
+
+    this->pin = NOT_ATTACHED;
+    this->timer = 0;
+    this->channel = TIMER_INVALID;
+    this->min = SERVO_DEFAULT_MIN_PW;
+    this->max = SERVO_DEFAULT_MAX_PW;
+
+    return true;
+}
+
+void Servo::write(unsigned int value) {
+    if (value < SERVO_MAX_WRITE_ANGLE) {
+        this->writeMicroseconds(ANGLE_TO_US(value));
+    } else {
+        this->writeMicroseconds(value);
+    }
+}
+
+void Servo::writeMicroseconds(uint16_t pulseWidth) {
+    if (this->pin == NOT_ATTACHED) {
+        ASSERT(0);
+        return;
+    }
+
+    pulseWidth = constrain(pulseWidth, this->min, this->max);
+    pwmWrite(this->pin, US_TO_COMPARE(pulseWidth));
+}
+
+int Servo::read() const {
+    if (this->pin == NOT_ATTACHED) {
+        ASSERT(0);
+        return 0;
+    }
+
+    unsigned int pw = this->readMicroseconds();
+    int a = US_TO_ANGLE(pw);
+    // map() round-trips in a weird way we correct for here
+    return a == 0 || a == 180 ? a : a + 1;
+}
+
+uint16_t Servo::readMicroseconds() const {
+    if (this->pin == NOT_ATTACHED) {
+        ASSERT(0);
+        return 0;
+    }
+
+    unsigned int compare = this->timer->getCompare(this->channel);
+    uint16_t c = COMPARE_TO_US(compare);
+    // map() round-trips in a weird way we correct for here
+    return c == 0 || c == 180 ? c : c + 1;
+}
diff --git a/libraries/Servo/Servo.h b/libraries/Servo/Servo.h
new file mode 100644
index 0000000..d35572a
--- /dev/null
+++ b/libraries/Servo/Servo.h
@@ -0,0 +1,116 @@
+/******************************************************************************
+ * The MIT License
+ *
+ * Copyright (c) 2010, LeafLabs, LLC.
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+ * THE SOFTWARE.
+ *****************************************************************************/
+
+#ifndef _SERVO_H_
+#define _SERVO_H_
+
+#include <stdint.h>
+
+#include "HardwareTimer.h"
+
+/* Note on Arduino compatibility:
+
+   In the Arduino implementation, PWM is done "by hand" in the sense
+   that timer channels are hijacked in groups and an ISR is set which
+   toggles Servo::attach()ed pins using digitalWrite().
+
+   While this scheme allows any pin to drive a servo, it chews up
+   cycles and complicates the programmer's notion of when a particular
+   timer channel will be in use.
+
+   This implementation only allows Servo instances to Servo::attach()
+   to pins that already have a timer channel associated with them, and
+   just uses pwmWrite() to drive the wave.
+
+   This introduces an incompatibility: while the Arduino
+   implementation of attach() returns the affected channel on success
+   and 0 on failure, this one returns true on success and false on
+   failure.
+
+   RC Servos expect a pulse every 20ms.  Since periods are set for
+   entire timers, rather than individual channels, attach()ing a Servo
+   to a pin can interfere with other pins associated with the same
+   timer.  As always, the pin mapping mega table is your friend.
+ */
+
+// Pin number of unattached pins
+#define NOT_ATTACHED (-1)
+
+// Maximum angle in degrees you can write(), exclusive.  Value chosen
+// for Arduino compatibility.
+#define SERVO_MAX_WRITE_ANGLE (200)
+
+// Default min (0 deg)/max(180 deg) pulse widths, in microseconds.
+// Value chosen for Arduino compatibility.
+#define SERVO_DEFAULT_MIN_PW (544)
+#define SERVO_DEFAULT_MAX_PW (2400)
+
+class Servo {
+public:
+    Servo();
+
+    /* Pin has to have a timer channel associated with it already;
+     * sets pinMode to PWM and returns true iff successful (failure
+     * when pin doesn't support PWM).  doesn't detach any ISRs
+     * associated with timer channel. */
+    bool attach(uint8_t pin);
+
+    /* Like attach(int), but with (inclusive) min (0 degree) and max
+     * (180 degree) pulse widths, in microseconds.
+     */
+    bool attach(uint8_t pin, uint16_t min, uint16_t max);
+
+    /* Return pin number if currently attach()ed to a pin,
+       NOT_ATTACHED otherwise. */
+    int attached() const { return pin; }
+
+    /* Stop driving the wave by disabling the output compare
+       interrupt.  Returns true if this call did anything. */
+    bool detach();
+
+    /* If value < MAX_WRITE_ANGLE, treated as an angle in degrees.
+       Otherwise, it's treated as a pulse width. */
+    void write(unsigned int value);
+
+    /* If outside of [min, max] determined by attach(), it is clamped
+       to lie in that range. */
+    void writeMicroseconds(uint16_t pulseWidth);
+
+    /* Return servo target angle, in degrees. This will lie between 0
+       and 180. */
+    int read() const;
+
+    /* Returns the current pulse width, in microseconds.  This will
+       lie within the [min, max] range. */
+    uint16_t readMicroseconds() const;
+
+private:
+    int8_t pin;
+    HardwareTimer *timer;
+    int channel;
+    uint16_t min;
+    uint16_t max;
+};
+
+#endif  /* _SERVO_H_ */
diff --git a/libraries/Servo/rules.mk b/libraries/Servo/rules.mk
new file mode 100644
index 0000000..13cd364
--- /dev/null
+++ b/libraries/Servo/rules.mk
@@ -0,0 +1,35 @@
+# Standard things
+sp := $(sp).x
+dirstack_$(sp) := $(d)
+d := $(dir)
+BUILDDIRS += $(BUILD_PATH)/$(d)
+
+# Local flags
+CFLAGS_$(d) := $(WIRISH_INCLUDES) $(LIBMAPLE_INCLUDES)
+
+# Local rules and targets
+cSRCS_$(d) :=
+
+# examples/UDPApp/udpapp.c \
+# examples/SocketApp/socketapp.c \
+# examples/WebClient/webclient.c \
+# examples/WebServer/webserver.c \
+# examples/Flash/webserver.c \
+
+cppSRCS_$(d) := Servo.cpp
+
+cFILES_$(d) := $(cSRCS_$(d):%=$(d)/%)
+cppFILES_$(d) := $(cppSRCS_$(d):%=$(d)/%)
+
+OBJS_$(d) := $(cFILES_$(d):%.c=$(BUILD_PATH)/%.o) \
+                 $(cppFILES_$(d):%.cpp=$(BUILD_PATH)/%.o)
+DEPS_$(d) := $(OBJS_$(d):%.o=%.d)
+
+$(OBJS_$(d)): TGT_CFLAGS := $(CFLAGS_$(d))
+
+TGT_BIN += $(OBJS_$(d))
+
+# Standard things
+-include $(DEPS_$(d))
+d := $(dirstack_$(sp))
+sp := $(basename $(sp))
\ No newline at end of file