Merge pull request #34 from emeb/master

Add Audio DAC example
cnlohr · Apr 12, 2023 · 3295854 · 3295854
2 parents a22976b + bc27534
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diff --git a/examples/spi_dac/.gdbinit b/examples/spi_dac/.gdbinit
@@ -0,0 +1,2 @@
+file tim1_pwm.elf
+target extended-remote localhost:3333
diff --git a/examples/spi_dac/Makefile b/examples/spi_dac/Makefile
@@ -0,0 +1,48 @@
+TARGET:=spi_dac
+
+all : flash
+
+PREFIX:=riscv64-unknown-elf
+
+GPIO_Toggle:=EXAM/GPIO/GPIO_Toggle/User
+
+CH32V003FUN:=../../ch32v003fun
+MINICHLINK:=../../minichlink
+
+ifeq ($(OS),Windows_NT)
+# On Windows, all the major RISC-V GCC installs are missing the -ec libgcc.
+LIB_GCC=../../misc/libgcc.a
+else
+LIB_GCC=-lgcc
+endif
+
+CFLAGS:= \
+	-g -Os -flto -ffunction-sections \
+	-static-libgcc $(LIB_GCC) \
+	-march=rv32ec \
+	-mabi=ilp32e \
+	-I/usr/include/newlib \
+	-I$(CH32V003FUN) \
+	-nostdlib \
+	-I. -DSTDOUT_UART -Wall
+
+LDFLAGS:=-T $(CH32V003FUN)/ch32v003fun.ld -Wl,--gc-sections
+
+SYSTEM_C:=$(CH32V003FUN)/ch32v003fun.c
+
+$(TARGET).elf : $(SYSTEM_C) $(TARGET).c
+	$(PREFIX)-gcc -o $@ $^ $(CFLAGS) $(LDFLAGS)
+
+$(TARGET).bin : $(TARGET).elf
+	$(PREFIX)-size $^
+	$(PREFIX)-objdump -S $^ > $(TARGET).lst
+	$(PREFIX)-objdump -t $^ > $(TARGET).map
+	$(PREFIX)-objcopy -O binary $< $(TARGET).bin
+	$(PREFIX)-objcopy -O ihex $< $(TARGET).hex
+
+flash : $(TARGET).bin
+	$(MINICHLINK)/minichlink -w $< flash -b
+
+clean :
+	rm -rf $(TARGET).elf $(TARGET).bin $(TARGET).hex $(TARGET).lst $(TARGET).map $(TARGET).hex
+
diff --git a/examples/spi_dac/README.md b/examples/spi_dac/README.md
@@ -0,0 +1,54 @@
+# SPI DAC Demo
+This example shows how to set up the SPI port with a timer, circular DMA and
+IRQs to do continuous audio output through an inexpensive I2S DAC.
+
+![Scope image of sine and sawtooth waves](oscope.png) 
+
+## Theory
+The CH32V003 does not have an I2S port which is usually required for driving
+audio DACs, but the inexpensive PT8211 stereo audio DAC is very forgiving of
+the signal format used to drive it so we can approximate an I2S signal using
+one of the CH32V003 on-chip timers to generate the frame sync signal. The SPI
+port then provides the bit clock and serial data.
+
+### Timer setup
+TIM1 on the CH32V003 is set up to generate a 48kHz square wave which is output
+on GPIO pin PC4 and serves as the frame sync or WS. The timer is configured to
+run in center-aligned mode 3 which generates DMA requests on both rising and
+falling edges. Channel 4 is configured as the output and the threshold is set
+to 50% and the overall period is set to 48kHz.
+
+### SPI setup
+SPI1 is configured for 16-bit TX with a bit clock of 48MHz/8 (3MHz) which is
+fast enough to clock out 16 bits of data between the edges of the frame sync
+signal. Transmit data arrives via DMA, but the SPI port does not control DMA -
+that is triggered from the timer above.
+
+### DMA setup
+DMA1 channel 4 is used because that channel is connected to TIM1 Chl 4 output
+and is set up in circular mode with both Half-transfer and Transfer-Complete
+interrupts. It continuously pulls data out of a 32-word buffer and sends it to
+the SPI port when the timer fires.
+
+### Interrupts
+The DMA TC and HT IRQs trigger execution of a buffer fill routine which simply
+indexes through a sinewave table at variable rates using fixed-point math to
+fill the buffer as requested. This process uses up only about 4% of the
+available CPU cycles so there's plenty leftover for foreground processing or
+more complex waveform calculations like interpolation or synthesis.
+
+## Use
+Connect a PT8211 DAC as follows:
+* DAC pin 1 (BCK) - MCU pin 15 (PC5/SCK)
+* DAC pin 2 (WS)  - MCU pin 14 (PC4/T1CH4)
+* DAC pin 3 (DIN) - MCU pin 16 {PC6/MOSI)
+* DAC pin 4 (GND) - ground
+* DAC pin 5 (VCC) - 3.3V or 5V supply
+* DAC pin 6 (LCH) - left channel output
+* DAC pin 8 (RCH) - right channel output
+
+![Schematic of SPI DAC hookup](spi_dac_schem.png)
+
+Connect an oscilloscope to the left and right channel outputs and observe a
+sine waveform at 187Hz on the right channel output and a sawtooth wave at
+47Hz on the left channel output.
diff --git a/examples/spi_dac/Sine16bit.h b/examples/spi_dac/Sine16bit.h
@@ -0,0 +1,259 @@
+/* Sinewave LUT */
+const int16_t Sine16bit[256] = {
+	      0,
+	    804,
+	   1608,
+	   2410,
+	   3212,
+	   4011,
+	   4808,
+	   5602,
+	   6393,
+	   7179,
+	   7962,
+	   8739,
+	   9512,
+	  10278,
+	  11039,
+	  11793,
+	  12539,
+	  13279,
+	  14010,
+	  14732,
+	  15446,
+	  16151,
+	  16846,
+	  17530,
+	  18204,
+	  18868,
+	  19519,
+	  20159,
+	  20787,
+	  21403,
+	  22005,
+	  22594,
+	  23170,
+	  23731,
+	  24279,
+	  24811,
+	  25329,
+	  25832,
+	  26319,
+	  26790,
+	  27245,
+	  27683,
+	  28105,
+	  28510,
+	  28898,
+	  29268,
+	  29621,
+	  29956,
+	  30273,
+	  30571,
+	  30852,
+	  31113,
+	  31356,
+	  31580,
+	  31785,
+	  31971,
+	  32137,
+	  32285,
+	  32412,
+	  32521,
+	  32609,
+	  32678,
+	  32728,
+	  32757,
+	  32767,
+	  32757,
+	  32728,
+	  32678,
+	  32609,
+	  32521,
+	  32412,
+	  32285,
+	  32137,
+	  31971,
+	  31785,
+	  31580,
+	  31356,
+	  31113,
+	  30852,
+	  30571,
+	  30273,
+	  29956,
+	  29621,
+	  29268,
+	  28898,
+	  28510,
+	  28105,
+	  27683,
+	  27245,
+	  26790,
+	  26319,
+	  25832,
+	  25329,
+	  24811,
+	  24279,
+	  23731,
+	  23170,
+	  22594,
+	  22005,
+	  21403,
+	  20787,
+	  20159,
+	  19519,
+	  18868,
+	  18204,
+	  17530,
+	  16846,
+	  16151,
+	  15446,
+	  14732,
+	  14010,
+	  13279,
+	  12539,
+	  11793,
+	  11039,
+	  10278,
+	   9512,
+	   8739,
+	   7962,
+	   7179,
+	   6393,
+	   5602,
+	   4808,
+	   4011,
+	   3212,
+	   2410,
+	   1608,
+	    804,
+	      0,
+	   -804,
+	  -1608,
+	  -2410,
+	  -3212,
+	  -4011,
+	  -4808,
+	  -5602,
+	  -6393,
+	  -7179,
+	  -7962,
+	  -8739,
+	  -9512,
+	 -10278,
+	 -11039,
+	 -11793,
+	 -12539,
+	 -13279,
+	 -14010,
+	 -14732,
+	 -15446,
+	 -16151,
+	 -16846,
+	 -17530,
+	 -18204,
+	 -18868,
+	 -19519,
+	 -20159,
+	 -20787,
+	 -21403,
+	 -22005,
+	 -22594,
+	 -23170,
+	 -23731,
+	 -24279,
+	 -24811,
+	 -25329,
+	 -25832,
+	 -26319,
+	 -26790,
+	 -27245,
+	 -27683,
+	 -28105,
+	 -28510,
+	 -28898,
+	 -29268,
+	 -29621,
+	 -29956,
+	 -30273,
+	 -30571,
+	 -30852,
+	 -31113,
+	 -31356,
+	 -31580,
+	 -31785,
+	 -31971,
+	 -32137,
+	 -32285,
+	 -32412,
+	 -32521,
+	 -32609,
+	 -32678,
+	 -32728,
+	 -32757,
+	 -32767,
+	 -32757,
+	 -32728,
+	 -32678,
+	 -32609,
+	 -32521,
+	 -32412,
+	 -32285,
+	 -32137,
+	 -31971,
+	 -31785,
+	 -31580,
+	 -31356,
+	 -31113,
+	 -30852,
+	 -30571,
+	 -30273,
+	 -29956,
+	 -29621,
+	 -29268,
+	 -28898,
+	 -28510,
+	 -28105,
+	 -27683,
+	 -27245,
+	 -26790,
+	 -26319,
+	 -25832,
+	 -25329,
+	 -24811,
+	 -24279,
+	 -23731,
+	 -23170,
+	 -22594,
+	 -22005,
+	 -21403,
+	 -20787,
+	 -20159,
+	 -19519,
+	 -18868,
+	 -18204,
+	 -17530,
+	 -16846,
+	 -16151,
+	 -15446,
+	 -14732,
+	 -14010,
+	 -13279,
+	 -12539,
+	 -11793,
+	 -11039,
+	 -10278,
+	  -9512,
+	  -8739,
+	  -7962,
+	  -7179,
+	  -6393,
+	  -5602,
+	  -4808,
+	  -4011,
+	  -3212,
+	  -2410,
+	  -1608,
+	   -804
+};
diff --git a/examples/spi_dac/debug.sh b/examples/spi_dac/debug.sh
@@ -0,0 +1,5 @@
+#!/bin/bash
+# before running this you should start OOCD server
+#../../../MRS_Toolchain_Linux_x64_V1.70/OpenOCD/bin/openocd -f ../../../MRS_Toolchain_Linux_x64_V1.70/OpenOCD/bin/wch-riscv.cfg
+
+../../../MRS_Toolchain_Linux_x64_V1.70/RISC-V\ Embedded\ GCC/bin/riscv-none-embed-gdb
diff --git a/examples/spi_dac/oscope.png b/examples/spi_dac/oscope.png