New PWM audio driver for audio output using a digital pin on a CPU

drivers/gaudio/pwm/driver.mk

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+# List the required driver.
+GFXSRC += $(GFXLIB)/drivers/gaudio/pwm/gaudio_play_lld.c
+
+# Required include directories
+GFXINC += $(GFXLIB)/drivers/gaudio/pwm

drivers/gaudio/pwm/gaudio_play_board_template.h

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+/*
+ * This file is subject to the terms of the GFX License. If a copy of
+ * the license was not distributed with this file, you can obtain one at:
+ *
+ *              http://ugfx.org/license.html
+ */
+
+#ifndef GAUDIO_PLAY_BOARD_H
+#define GAUDIO_PLAY_BOARD_H
+
+/*
+ * This routine is defined in the driver - the timer interrupt should call this routine.
+ *
+ * static void gaudio_play_pwm_timer_callbackI(void);
+ *
+ */
+
+static bool gaudio_play_pwm_setup(uint32_t frequency, ArrayDataFormat format) {
+	/* Initialise the PWM - use a midpoint value for the initial PWM value */
+	/* Initialise the timer interrupt @ frequency */
+	/* Return FALSE if any parameter invalid */
+}
+
+static void gaudio_play_pwm_start(void) {
+	/* Start the PWM  */
+	/* Start the timer interrupt */
+}
+
+static void gaudio_play_pwm_stop(void) {
+	/* Stop the timer interrupt */
+	/* Stop the PWM */
+}
+
+static void gaudio_play_pwm_setI(uint16_t value) {
+	/* Set the PWM value */
+}
+
+#endif	/* GAUDIO_PLAY_BOARD_H */

drivers/gaudio/pwm/gaudio_play_config.h

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+/*
+ * This file is subject to the terms of the GFX License. If a copy of
+ * the license was not distributed with this file, you can obtain one at:
+ *
+ *              http://ugfx.org/license.html
+ */
+
+#ifndef GAUDIO_PLAY_CONFIG_H
+#define GAUDIO_PLAY_CONFIG_H
+
+#if GFX_USE_GAUDIO && GAUDIO_NEED_PLAY
+
+/*===========================================================================*/
+/* Driver hardware support.                                                  */
+/*===========================================================================*/
+
+/* These may need to change for your hardware. If so copy this file to your
+ * project directory and then alter it.
+ * The maximum sample frequency should be less than
+ * 		Max PWM Clock / (2 ^ Bits per sample)
+ * eg. For the AT91SAM7 max PWM clock = 48MHz / 2
+ * For 10 bit PWM accuracy that means GAUDIO_PLAY_MAX_SAMPLE_FREQUENCY = 23,437 Hz
+ */
+#define GAUDIO_PLAY_MAX_SAMPLE_FREQUENCY		22000
+#define GAUDIO_PLAY_NUM_FORMATS					2
+#define GAUDIO_PLAY_FORMAT1						ARRAY_DATA_10BITUNSIGNED
+#define GAUDIO_PLAY_FORMAT2						ARRAY_DATA_8BITUNSIGNED
+#define GAUDIO_PLAY_NUM_CHANNELS				1
+#define GAUDIO_PLAY_CHANNEL0_IS_STEREO			FALSE
+#define	GAUDIO_PLAY_MONO						0
+
+#endif	/* GFX_USE_GAUDIO && GAUDIO_NEED_PLAY */
+
+#endif	/* GAUDIO_PLAY_CONFIG_H */

drivers/gaudio/pwm/gaudio_play_lld.c

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+/*
+ * This file is subject to the terms of the GFX License. If a copy of
+ * the license was not distributed with this file, you can obtain one at:
+ *
+ *              http://ugfx.org/license.html
+ */
+
+#include "gfx.h"
+
+#if GFX_USE_GAUDIO && GAUDIO_NEED_PLAY
+
+/* Include the driver defines */
+#include "src/gaudio/driver_play.h"
+
+/* Forward definition */
+static void gaudio_play_pwm_timer_callbackI(void);
+
+/* Include the board interface */
+#include "gaudio_play_board.h"
+
+static GDataBuffer		*pplay;
+static ArrayDataFormat	playfmt;
+static size_t			playlen;
+static uint8_t			*pdata;
+
+static void gaudio_play_pwm_timer_callbackI(void) {
+	if (pplay) {
+
+		// Get the next value from the current data buffer
+		if (gfxSampleFormatBits(playfmt) > 8) {
+			gaudio_play_pwm_setI(*(uint16_t *)pdata);
+			pdata += 2;
+		} else {
+			gaudio_play_pwm_setI(*pdata);
+			pdata++;
+		}
+
+		// Are we done yet
+		if (--playlen)
+			return;
+		gaudioPlayReleaseDataBlockI(pplay);
+
+		// Get a new data buffer
+		if (!(pplay = gaudioPlayGetDataBlockI())) {
+			// All is done
+			gaudioPlayDoneI();
+			return;
+		}
+
+	} else {
+		// Get a new data buffer
+		if (!(pplay = gaudioPlayGetDataBlockI()))
+			return;
+	}
+
+	// Set up ready for the new buffer
+	playlen = pplay->len;
+	if (gfxSampleFormatBits(playfmt) > 8)
+		playlen >>= 1;
+	pdata = (uint8_t *)(pplay+1);
+}
+
+
+/*===========================================================================*/
+/* External declarations.                                                    */
+/*===========================================================================*/
+
+bool_t gaudio_play_lld_init(uint16_t channel, uint32_t frequency, ArrayDataFormat format) {
+	(void) channel;
+
+	if (format != ARRAY_DATA_8BITUNSIGNED && format != ARRAY_DATA_10BITUNSIGNED)
+		return FALSE;
+
+	playfmt = format;
+	return gaudio_play_pwm_setup(frequency, format);
+}
+
+bool_t gaudio_play_lld_set_volume(uint8_t vol) {
+	(void) vol;
+	return FALSE;
+}
+
+void gaudio_play_lld_start(void) {
+
+	gfxSystemLock();
+	// Get a new data buffer
+	if (pplay || !(pplay = gaudioPlayGetDataBlockI())) {
+		gfxSystemUnlock();			// Nothing to do
+		return;
+	}
+
+	// Set up ready for the new buffer
+	playlen = pplay->len;
+	if (gfxSampleFormatBits(playfmt) > 8)
+		playlen >>= 1;
+	pdata = (uint8_t *)(pplay+1);
+	gfxSystemUnlock();
+
+	// Start the playing
+	gaudio_play_pwm_start();
+}
+
+void gaudio_play_lld_stop(void) {
+	// Stop everything
+	gaudio_play_pwm_stop();
+
+	// We may need to clean up the remaining buffer.
+	gfxSystemLock();
+	if (pplay) {
+		gaudioPlayReleaseDataBlockI(pplay);
+		pplay = 0;
+		gaudioPlayDoneI();
+	}
+	gfxSystemUnlock();
+}
+
+#endif /* GFX_USE_GAUDIO && GAUDIO_NEED_PLAY */

drivers/gaudio/pwm/readme.txt

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+This driver uses a PWM output and a timer to implement an audio play channel.
+
+Whilst the default config settings will probably work for your hardware, you may need to change them.
+If so copy gaudio_play_config.h to your project directory and then alter it.
+
+The maximum sample frequency is governed primarily by the number of bits of resolution and the
+maximum PWM clock rate. The maximum sample frequency should be less than...
+
+	Max PWM Clock / (2 ^ Bits per sample)
+	
+eg. For the AT91SAM7 max PWM clock = 48MHz / 2
+	For 10 bit PWM accuracy that means GAUDIO_PLAY_MAX_SAMPLE_FREQUENCY = 23,437 Hz