mbedPi

Diff: source/PwmOut.cpp

Revision:

1:1f2d9982fa8c

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/source/PwmOut.cpp	Tue Dec 20 12:08:07 2022 +0000
@@ -0,0 +1,210 @@
+#include "mbed.h"
+#include "math.h"
+
+extern volatile uint32_t *bcm2835_pwm;
+extern volatile uint32_t *bcm2835_clk;
+
+/********************************************************************
+ *
+ *  PwmOut
+ *
+ ********************************************************************/
+/** Create a PwmOut connected to the specified pin
+ *
+ *  @param pin PwmOut pin to connect to
+ */
+PwmOut::PwmOut(PinName pin) :
+    _pwmPin(pin),
+    _duty_cycle(0)
+{
+    // Set the output pin to Alt Fun 5, to allow PWM channel 0 to be output there
+    bcm2835_gpio_fsel(_pwmPin, BCM2835_GPIO_FSEL_ALT5);
+    // Set default PWM period to 20ms (usually used by servos)
+    period_ms(20);
+}
+
+/**
+ * @brief
+ * @note
+ * @param
+ * @retval
+ */
+PwmOut::~PwmOut()
+{
+    bcm2835_gpio_fsel(_pwmPin, BCM2835_GPIO_FSEL_INPT);
+}
+
+/** Set the output duty-cycle, specified as a percentage (float)
+ *
+ *  @param value A floating-point value representing the output duty-cycle,
+ *    specified as a percentage. The value should lie between
+ *    0.0f (representing on 0%) and 1.0f (representing on 100%).
+ *    Values outside this range will be saturated to 0.0f or 1.0f.
+ */
+void PwmOut::write(float value)
+{
+    _duty_cycle = value;
+
+    if (value < 0) {
+        _duty_cycle = 0;
+    }
+
+    if (value > 1.0) {
+        _duty_cycle = 1.0;
+    }
+
+    bcm2835_pwm_set_data(PWM_CHANNEL, _duty_cycle * _range);
+    bcm2835_pwm_set_mode(PWM_CHANNEL, 1, 1);    // channel, MARKSPACE mode, active
+}
+
+/** Return the current output duty-cycle setting, measured as a percentage (float)
+ *
+ *  @returns
+ *    A floating-point value representing the current duty-cycle being output on the pin,
+ *    measured as a percentage. The returned value will lie between
+ *    0.0f (representing on 0%) and 1.0f (representing on 100%).
+ *
+ *  @note
+ *  This value may not match exactly the value set by a previous write().
+ */
+float PwmOut::read()
+{
+    return _duty_cycle;
+}
+
+/** Set the PWM period, specified in bcm2835PWMPulseWidth (micro/nano seconds), keeping the duty cycle the same.
+ *  @note  Sets clock divider according to the required period.
+ *  @param period Change the period of a PWM signal. The allowed values are:
+ *         BCM2835_PWM_PERIOD_833_NS  ->  833.33 ns  = 1200.000  kHz
+ */
+void PwmOut::period_ms(int period_ms)
+{
+    _range = period_ms * 1200;
+    bcm2835_pwm_set_clock(BCM2835_PWM_PERIOD_833_NS);   // clock pulse = 833.33 ns
+    bcm2835_pwm_set_range(PWM_CHANNEL, _range);
+}
+
+/** Set the PWM period, specified in bcm2835PWMPulseWidth (micro/nano seconds), keeping the duty cycle the same.
+ *  @note  Sets clock divider according to the required period.
+ *  @param period Change the period of a PWM signal. The allowed values are:
+ *         BCM2835_PWM_PERIOD_104_NS  -> 104.16 ns  = 9600.000  kHz
+ */
+void PwmOut::period_us(int period_us)
+{
+    _range = rintf(period_us * 9.600f);
+    bcm2835_pwm_set_clock(BCM2835_PWM_PERIOD_104_NS);
+    bcm2835_pwm_set_range(PWM_CHANNEL, _range);
+}
+
+/***********************************************************************
+ *
+ *  PWM
+ *
+ ***********************************************************************/
+
+/*! Sets the PWM clock divisor,
+  to control the basic PWM pulse widths.
+  \param[in] divisor Divides the basic 19.2MHz PWM clock. You can use one of the common
+  values BCM2835_PWM_CLOCK_DIVIDER_* in \ref bcm2835PWMClockDivider
+*/
+void bcm2835_pwm_set_clock(uint32_t divisor)
+{
+    if (bcm2835_clk == MAP_FAILED || bcm2835_pwm == MAP_FAILED) {
+        return;         /* bcm2835_init() failed or not root */
+    }
+
+    /* From Gerts code */
+    divisor &= 0xfff;
+
+    /* Stop PWM clock */
+    bcm2835_peri_write(bcm2835_clk + BCM2835_PWMCLK_CNTL, BCM2835_PWM_PASSWRD | 0x01);
+    bcm2835_delay(110); /* Prevents clock going slow */
+
+    /* Wait for the clock to be not busy */
+    while ((bcm2835_peri_read(bcm2835_clk + BCM2835_PWMCLK_CNTL) & 0x80) != 0)
+        bcm2835_delay(1);
+
+    /* set the clock divider and enable PWM clock */
+    bcm2835_peri_write(bcm2835_clk + BCM2835_PWMCLK_DIV, BCM2835_PWM_PASSWRD | (divisor << 12));
+    bcm2835_peri_write(bcm2835_clk + BCM2835_PWMCLK_CNTL, BCM2835_PWM_PASSWRD | 0x11);  /* Source=osc and enable */
+}
+
+/*! Sets the mode of the given PWM channel,
+  allowing you to control the PWM mode and enable/disable that channel
+  \param[in] channel The PWM channel. 0 or 1.
+  \param[in] markspace Set true if you want Mark-Space mode. 0 for Balanced mode.
+  \param[in] enabled Set true to enable this channel and produce PWM pulses.
+*/
+void bcm2835_pwm_set_mode(uint8_t channel, uint8_t markspace, uint8_t enabled)
+{
+    if (bcm2835_clk == MAP_FAILED || bcm2835_pwm == MAP_FAILED) {
+        return; /* bcm2835_init() failed or not root */
+    }
+
+    /* If you use the barrier here, wierd things happen, and the commands dont work */
+
+    /*
+    uint32_t    control = bcm2835_peri_read(bcm2835_pwm + BCM2835_PWM_CONTROL);
+
+    if (channel == 0) {
+        if (markspace)
+            control |= BCM2835_PWM0_MS_MODE;
+        else
+            control &= ~BCM2835_PWM0_MS_MODE;
+        if (enabled)
+            control |= BCM2835_PWM0_ENABLE;
+        else
+            control &= ~BCM2835_PWM0_ENABLE;
+    }
+    else
+    if (channel == 1) {
+        if (markspace)
+            control |= BCM2835_PWM1_MS_MODE;
+        else
+            control &= ~BCM2835_PWM1_MS_MODE;
+        if (enabled)
+            control |= BCM2835_PWM1_ENABLE;
+        else
+            control &= ~BCM2835_PWM1_ENABLE;
+    }
+
+    bcm2835_peri_write_nb(bcm2835_pwm + BCM2835_PWM_CONTROL, control);
+    */
+
+    bcm2835_peri_write_nb(bcm2835_pwm + BCM2835_PWM_CONTROL, BCM2835_PWM0_ENABLE | BCM2835_PWM1_ENABLE | BCM2835_PWM0_MS_MODE | BCM2835_PWM1_MS_MODE);
+}
+
+/*! Sets the maximum range of the PWM output.
+  The data value can vary between 0 and this range to control PWM output
+  \param[in] channel The PWM channel. 0 or 1.
+  \param[in] range The maximum value permitted for DATA.
+*/
+void bcm2835_pwm_set_range(uint8_t channel, uint32_t range)
+{
+    if (bcm2835_clk == MAP_FAILED || bcm2835_pwm == MAP_FAILED)
+        return; /* bcm2835_init() failed or not root */
+
+    if (channel == 0)
+        bcm2835_peri_write_nb(bcm2835_pwm + BCM2835_PWM0_RANGE, range);
+    else
+    if (channel == 1)
+        bcm2835_peri_write_nb(bcm2835_pwm + BCM2835_PWM1_RANGE, range);
+}
+
+/*! Sets the PWM pulse ratio to emit to DATA/RANGE,
+  where RANGE is set by bcm2835_pwm_set_range().
+  \param[in] channel The PWM channel. 0 or 1.
+  \param[in] data Controls the PWM output ratio as a fraction of the range.
+  Can vary from 0 to RANGE.
+*/
+void bcm2835_pwm_set_data(uint8_t channel, uint32_t data)
+{
+    if (bcm2835_clk == MAP_FAILED || bcm2835_pwm == MAP_FAILED)
+        return; /* bcm2835_init() failed or not root */
+
+    if (channel == 0)
+        bcm2835_peri_write_nb(bcm2835_pwm + BCM2835_PWM0_DATA, data);
+    else
+    if (channel == 1)
+        bcm2835_peri_write_nb(bcm2835_pwm + BCM2835_PWM1_DATA, data);
+}