From 68166dc6a07c2b2502e3eef2e78dae642dfb29ff Mon Sep 17 00:00:00 2001
From: cnlohr <lohr85@gmail.com>
Date: Sun, 17 Nov 2024 17:14:43 -0800
Subject: [PATCH] Add example for timer capture.

---
 examples/tim1_capture_dma/Makefile           | 10 +++
 examples/tim1_capture_dma/funconfig.h        |  7 ++
 examples/tim1_capture_dma/tim1_capture_dma.c | 88 ++++++++++++++++++++
 3 files changed, 105 insertions(+)
 create mode 100644 examples/tim1_capture_dma/Makefile
 create mode 100644 examples/tim1_capture_dma/funconfig.h
 create mode 100644 examples/tim1_capture_dma/tim1_capture_dma.c

diff --git a/examples/tim1_capture_dma/Makefile b/examples/tim1_capture_dma/Makefile
new file mode 100644
index 00000000..835910e5
--- /dev/null
+++ b/examples/tim1_capture_dma/Makefile
@@ -0,0 +1,10 @@
+all : flash
+
+TARGET:=tim1_capture_dma
+CH32V003FUN:=../../ch32v003fun
+
+include ../../ch32v003fun/ch32v003fun.mk
+
+flash : cv_flash
+clean : cv_clean
+
diff --git a/examples/tim1_capture_dma/funconfig.h b/examples/tim1_capture_dma/funconfig.h
new file mode 100644
index 00000000..998cf76f
--- /dev/null
+++ b/examples/tim1_capture_dma/funconfig.h
@@ -0,0 +1,7 @@
+#ifndef _FUNCONFIG_H
+#define _FUNCONFIG_H
+
+#define CH32V003           1
+
+#endif
+
diff --git a/examples/tim1_capture_dma/tim1_capture_dma.c b/examples/tim1_capture_dma/tim1_capture_dma.c
new file mode 100644
index 00000000..8448f906
--- /dev/null
+++ b/examples/tim1_capture_dma/tim1_capture_dma.c
@@ -0,0 +1,88 @@
+// Example using Timer 1 capture to look for down-going events
+// on PD2.  Then using DMA to capture that event and write it
+// to a circular queue that can be read out later.
+//
+// For it to produce interesting output, you can wire PD2 to PD3.
+
+#include "ch32v003fun.h"
+#include <stdio.h>
+
+uint32_t count;
+uint16_t reply_buffer[256]; // For generating the mask/modulus, this must be a power of 2 size.
+
+int main()
+{
+	SystemInit();
+	funGpioInitAll();
+
+	// Enable GPIOs
+	RCC->APB2PCENR |= RCC_APB2Periph_TIM1 | RCC_APB2Periph_AFIO;
+	RCC->AHBPCENR |= RCC_AHBPeriph_DMA1;
+
+	// TIM2_CH1 -> PD2 -> DMA1_CH2
+	#define DMA_IN  DMA1_Channel2
+
+	// T1C1 -> What we are sampling.
+	funPinMode( PD2, GPIO_CFGLR_IN_PUPD );
+	funDigitalWrite( PD2, 1 );
+
+	// PD3 output to send something back into PD2.
+	funPinMode( PD3, GPIO_CFGLR_OUT_2Mhz_PP );
+
+	TIM1->PSC = 0x0fff;		// set TIM1 clock prescaler divider (Massive prescaler)
+	TIM1->ATRLR = 65535;	// set PWM total cycle width
+
+	// CH2 Mode is output, PWM1 (CC1S = 00, OC1M = 110)
+	TIM1->CHCTLR1 = TIM_CC1S_0;
+
+	// Add here CC1P to switch from UP->GOING to DOWN->GOING log times.
+	TIM1->CCER = TIM_CC1E;// | TIM_CC1P;
+	
+	// initialize counter
+	TIM1->SWEVGR = TIM_UG;
+
+	// Enable TIM2
+	TIM1->CTLR1 = TIM_ARPE | TIM_CEN;
+	TIM1->DMAINTENR = TIM_CC1DE | TIM_UDE; // Enable DMA motion.
+	TIM1->CTLR1 |= TIM_URS;   // Trigger DMA on overflow ONLY.
+
+	// TIM1_TRIG/TIM1_COM/TIM1_CH4
+	DMA_IN->MADDR = (uint32_t)reply_buffer;
+	DMA_IN->PADDR = (uint32_t)&TIM1->CH1CVR; // Input
+	DMA_IN->CFGR = 
+		0                 |                  // PERIPHERAL to MEMORY
+		0                 |                  // Low priority.
+		DMA_CFGR1_MSIZE_0 |                  // 16-bit memory
+		DMA_CFGR1_PSIZE_0 |                  // 16-bit peripheral
+		DMA_CFGR1_MINC    |                  // Increase memory.
+		DMA_CFGR1_CIRC    |                  // Circular mode.
+		0                 |                  // NO Half-trigger
+		0                 |                  // NO Whole-trigger
+		DMA_CFGR1_EN;                        // Enable
+
+	int samples_in_buffer = sizeof(reply_buffer) / sizeof(reply_buffer[0]);
+	DMA_IN->CNTR = samples_in_buffer;
+
+	int tail = 0;
+	while(1)
+	{
+		// Must perform modulus here, in case DMA_IN->CNTR == 0.
+		int head = (samples_in_buffer - DMA_IN->CNTR) & (samples_in_buffer-1);
+
+		while( head != tail )
+		{
+			uint32_t time_of_event = reply_buffer[tail];
+			printf( "%d/%d %d\n", tail, head, (int)time_of_event );
+
+			// Performs modulus to loop back.
+			tail = (tail+1)&(samples_in_buffer-1);
+		}
+
+		Delay_Ms(100);
+		funDigitalWrite( PD3, 1 );
+		Delay_Ms(10);
+		funDigitalWrite( PD3, 0 );
+		printf( "." );
+	}
+}
+