Add stm32f411e-discovery I2S example sound_out.

This plays a sine wave through the audio jack.

Author: Kalle Raiskila

examples/stm32/f4/stm32f411e-discovery/README.md

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+# README
+
+This directory contains samples for the STM32F411EDISCOVERY
+board. This is similar to the original STM32F4DISCOVERY, but
+has the the STM32F411VE MCU.
+The board is labeled 'MB-1115 B-02'
+

examples/stm32/f4/stm32f411e-discovery/sound_out/Makefile

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+BINARY = sound_out
+DEVICE=STM32F411VE
+include ../../Makefile.include
+

examples/stm32/f4/stm32f411e-discovery/sound_out/README.md

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+# README
+
+This example demonstrates using the oboard audio DAC on
+STM32F411-Discovery board.
+It plays a continuous 1 kHz sine wave.
+
+## Board connections
+
+Sepeakers attached to the 3.5mm audio jack.
+Note: volume is turned low, but beware of loud sounds
+in case of bugs (i.e. plug the headphones to your ear
+only after playback starts!)
+
+## DMA mode
+
+There is a compile-time option (#define USE_DMA) that
+demonstrates how to have the DMA engine write audio
+data to the DAC.
+
+## LEDs
+
+Both versions of the program blink the orange
+led (PD13) at ~0.5Hz. The DMA version toggles the
+green led (PD12) on every DMA interrupt, which means
+the pattern is visible with oscilloscope only (500Hz).

examples/stm32/f4/stm32f411e-discovery/sound_out/sound_out.c

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+/*
+ * Example for how to use I2C and I2S with libopencm3.
+ * This is intended for the STM32F411-Discovery demoboard.
+ *
+ * The device plays a 1kHz sine through the audio jack.
+ */
+
+/* Compile time option to use DMA to feed audio to the I2S.
+ * Without this, the audio is sent by polling the I2S peripheral's
+ * TXE bit */
+#define USE_DMA
+
+
+#include <libopencm3/stm32/gpio.h>
+#include <libopencm3/stm32/i2c.h>
+#include <libopencm3/stm32/rcc.h>
+#include <libopencm3/stm32/spi.h>
+
+#ifdef USE_DMA
+#include <libopencm3/cm3/nvic.h>
+#include <libopencm3/stm32/dma.h>
+#endif
+
+
+/* Test audio: 8 points of a sine.
+ * At Fs=8kHz, this means a 1kHz audio sine
+ * (the other channel is mute)
+ */
+#define VOL 0x0020
+#define D16(x) ((int16_t)(x*VOL) )
+int16_t audio[16]=
+{ D16(0),       0,
+  D16(0.70711), 0,
+  D16(1),       0,
+  D16(0.70711), 0,
+  D16(0),       0,
+  D16(-0.70711),0,
+  D16(-0.9999), 0,
+  D16(-0.707),  0 };
+
+
+static void write_i2c_to_audiochip( uint8_t reg, uint8_t contents)
+{
+	uint8_t packet[2];
+	packet[0] = reg;
+	packet[1] = contents;
+	/* STM32F411 discovery user's manual gives device address with R/W bit,
+	 * libopencm3 wants the address without it. */
+	uint8_t address = (0x94)>>1;
+
+	i2c_transfer7(I2C1, address, packet, 2, NULL, 0);
+}
+
+#ifdef USE_DMA
+/* Interrupt service routine for the DMA.
+ * The name is "magic" and suffices as installation hook into libopencm3. */
+void dma1_stream5_isr(void)
+{
+	gpio_toggle(GPIOD, GPIO12);
+
+	/* Clear the 'transfer complete' interrupt, or execution would jump right back to this ISR. */
+	if (dma_get_interrupt_flag(DMA1, DMA_STREAM5, DMA_TCIF)) {
+		dma_clear_interrupt_flags(DMA1, DMA_STREAM5, DMA_TCIF);
+	}
+}
+#endif
+
+int main(void)
+{
+	/* Set device clocks from opencm3 provided preset.*/
+	const struct rcc_clock_scale *clocks = &rcc_hsi_configs[RCC_CLOCK_3V3_84MHZ];
+	rcc_clock_setup_pll( clocks );
+
+	rcc_periph_clock_enable(RCC_GPIOA);
+	rcc_periph_clock_enable(RCC_GPIOB);
+	rcc_periph_clock_enable(RCC_GPIOC);
+	rcc_periph_clock_enable(RCC_GPIOD);
+
+	/* Initialize "heartbeat" LED GPIOs. */
+#ifdef USE_DMA
+	gpio_mode_setup(GPIOD, GPIO_MODE_OUTPUT, GPIO_PUPD_NONE, GPIO12); /* green led */
+#endif
+	gpio_mode_setup(GPIOD, GPIO_MODE_OUTPUT, GPIO_PUPD_NONE, GPIO13); /* orange led */
+
+
+	/* Initialize I2C.
+	 * I2C is needed to initialize the onboard audio DAC chip.
+	 * PB6 - SCL (I2C clock)
+	 * PB9 - SDA (I2C data)
+	 * The board does not have pullups on the I2C lines, so
+	 * we use the chip internal pullups.
+	 * Also the pins must be open drain, as per I2C specification.
+	 * STM32F411 datasheet "Alternate Functions table" tells that
+	 * I2C is AlternateFucntion 4 for both pins.
+	 */
+	gpio_mode_setup(GPIOB, GPIO_MODE_AF, GPIO_PUPD_PULLUP, GPIO6);
+	gpio_mode_setup(GPIOB, GPIO_MODE_AF, GPIO_PUPD_PULLUP, GPIO9);
+	gpio_set_output_options(GPIOB, GPIO_OTYPE_OD, GPIO_OSPEED_25MHZ, GPIO6);
+	gpio_set_output_options(GPIOB, GPIO_OTYPE_OD, GPIO_OSPEED_25MHZ, GPIO9);
+	gpio_set_af(GPIOB, GPIO_AF4, GPIO6);
+	gpio_set_af(GPIOB, GPIO_AF4, GPIO9);
+
+	/* Initialize the I2C itself.
+	 * Since we are master, we would not need to initialize slave
+	 * address, but this is the only libopencm3 API call that sets
+	 * the 'bit14 of CCR' - a bit in the I2C that is HW reset to 0,
+	 * but manual says 'must be 1' */
+	rcc_periph_clock_enable(RCC_I2C1);
+	i2c_peripheral_disable(I2C1);
+	i2c_set_speed(I2C1, i2c_speed_sm_100k, clocks->apb1_frequency/1000000);
+	i2c_set_own_7bit_slave_address(I2C1, 0);
+	i2c_peripheral_enable(I2C1);
+
+
+	/* Initialize I2S.
+	 * I2S is implemented as a HW mode of the SPI peripheral.
+	 * Since this is a STM32F411, there is a separate I2S PLL
+	 * that needs to be enabled.
+	 */
+	rcc_osc_on(RCC_PLLI2S);
+	rcc_periph_clock_enable(RCC_SPI3);
+	i2s_disable(SPI3);
+	i2s_set_standard(SPI3, i2s_standard_philips);
+	i2s_set_dataformat(SPI3, i2s_dataframe_ch16_data16);
+	i2s_set_mode(SPI3, i2s_mode_master_transmit);
+	i2s_masterclock_enable(SPI3);
+	/* RCC_PLLI2SCFGR is left at reset value: 0x24003010 i.e.
+	 * PLLR = 2
+	 * PLLI2SN = 192
+	 * PLLI2SM = 16
+	 * And since the input is PLL source (i.e. HSI = 16MHz)
+	 * The I2S clock = 16 / 16 * 192 / 2 = 96MHz
+	 * Calculate sampling frequency from equation given in
+	 * STM32F411 reference manual:
+	 * Fs = I2Sclk/ (32*2 * ((2*I2SDIV)+ODD)*4)
+	 * I2SDIV = I2Sclk/(512*Fs)
+	 * Fs=8kHz => I2SDIV=23,4 so 23 + ODD bit set
+	 */
+	i2s_set_clockdiv(SPI3, 23, 1);
+#ifdef USE_DMA
+	/* Have the SPI/I2S peripheral ping the DMA each time data is sent.
+	 * The DMA peripheral is configured later. */
+	spi_enable_tx_dma(SPI3);
+#endif
+	i2s_enable(SPI3);
+
+	/* I2S pins:
+	 * Master clock: PC7
+	 * Bit clock: PC10
+	 * Data: PC12
+	 * L/R clock: PA4
+	 */
+	gpio_mode_setup(GPIOC, GPIO_MODE_AF, GPIO_PUPD_NONE, GPIO7);
+	gpio_set_af(GPIOC, GPIO_AF6, GPIO7);
+	gpio_mode_setup(GPIOC, GPIO_MODE_AF, GPIO_PUPD_NONE, GPIO10);
+	gpio_set_af(GPIOC, GPIO_AF6, GPIO10);
+	gpio_mode_setup(GPIOC, GPIO_MODE_AF, GPIO_PUPD_NONE, GPIO12);
+	gpio_set_af(GPIOC, GPIO_AF6, GPIO12);
+	gpio_mode_setup(GPIOA, GPIO_MODE_AF, GPIO_PUPD_NONE, GPIO4);
+	gpio_set_af(GPIOA, GPIO_AF6, GPIO4);
+
+
+	/* Initialize the Audio DAC, as per its datasheet.
+	 * CS43L22 /RESET is connected to PD4, first release it. Then write
+	 * minimum set of needed settings. */
+	gpio_mode_setup(GPIOD, GPIO_MODE_OUTPUT, GPIO_PUPD_NONE, GPIO4);
+	gpio_set(GPIOD, GPIO4);
+	write_i2c_to_audiochip(0x06, 0x04); // interface control 1: set I2S dataformat
+	write_i2c_to_audiochip(0x02, 0x9e); // power control 1: Magic value to power up the chip
+
+
+#ifdef USE_DMA
+	/* Enable DMA from memory to I2S peripheral.
+	 * The DMA is configured as circular, i.e. it restarts automatically when
+	 * the requested amount of datasamples are set.
+	 * SPI3/I2S3 is available on DMA1 stream 5, channel 0 (see RM 0383, table 27) */
+	rcc_periph_clock_enable(RCC_DMA1);
+	nvic_enable_irq(NVIC_DMA1_STREAM5_IRQ);
+	dma_disable_stream(DMA1, DMA_STREAM5);
+	dma_set_priority(DMA1, DMA_STREAM5, DMA_SxCR_PL_HIGH);
+	dma_set_memory_size(DMA1, DMA_STREAM5, DMA_SxCR_MSIZE_16BIT);
+	dma_set_peripheral_size(DMA1, DMA_STREAM5, DMA_SxCR_PSIZE_16BIT);
+	dma_enable_memory_increment_mode(DMA1, DMA_STREAM5);
+	dma_enable_circular_mode(DMA1, DMA_STREAM5);
+	dma_set_transfer_mode(DMA1, DMA_STREAM5, DMA_SxCR_DIR_MEM_TO_PERIPHERAL);
+	dma_set_peripheral_address(DMA1, DMA_STREAM5, (uint32_t) &SPI_DR(SPI3));
+	dma_set_memory_address(DMA1, DMA_STREAM5, (uint32_t) audio);
+	dma_set_number_of_data(DMA1, DMA_STREAM5, sizeof(audio)/sizeof(audio[0]));
+	dma_enable_transfer_complete_interrupt(DMA1, DMA_STREAM5);
+	dma_channel_select(DMA1, DMA_STREAM5, DMA_SxCR_CHSEL_0);
+	dma_enable_stream(DMA1, DMA_STREAM5);
+#endif
+
+
+	while(1) {
+		/* Blink the heartbeat LED at ~0,5Hz*/
+#ifdef USE_DMA
+		const int blinkslowdown = 20e6;
+#else
+		const int blinkslowdown = 1000;
+#endif
+		static int i=0;
+		if( ++i > blinkslowdown) {
+			gpio_toggle(GPIOD, GPIO13);
+			i=0;
+		}
+
+#ifndef USE_DMA
+		/* Blocking send of the data buffer */
+		for( unsigned j=0; j < sizeof(audio)/sizeof(audio[0]); j++)
+			spi_send(SPI3, audio[j]);
+#endif
+	}
+	return 0;
+}
+