Include ADC-assisted-touch on CH32V003 example, using direct RC slope measurement.

examples/cap_touch_adc/Makefile

+all : flash
+
+TARGET:=cap_touch_adc
+
+include ../../ch32v003fun/ch32v003fun.mk
+
+flash : cv_flash
+clean : cv_clean
+
+

examples/cap_touch_adc/cap_touch_adc.c

+/*
+	Copyright (c) 2023 Valve Corporation (see copyright notice at bottom)
+
+	ADC-aided capacitive touch sensing.
+
+	This demonstrates use of the ADC with cap sense pads. By using the ADC, you
+	can get much higher resolution than if you use the exti.  But, you are
+	limited by the number of ADC lines, i.e. you can only support a maximum of
+	eight (8) touch inputs with this method.
+
+	In exchange for that, typically you can get > 1,000 LSBs per 1 CM^2 and it
+	can convert faster.  Carefully written code can be as little as 2us per
+	conversion!
+
+	The mechanism of operation for the touch sensing on the CH32V003 is to:
+		* Hold an IO low.
+		* Start the ADC
+		* Use the internal pull-up to pull the line high.
+		* The ADC will sample the voltage on the slope.
+		* Lower voltage = longer RC respone, so higher capacitance. 
+*/
+
+#include "ch32v003fun.h"
+#include <stdio.h>
+
+#define ADC_SAMPLE_TIME 2  // Tricky: Don't change this without a lot of experimentation.
+#define MAX_SCALECHECK  4
+void InitTouchADC( )
+{
+	// ADCCLK = 24 MHz => RCC_ADCPRE = 0: divide sys clock by 2
+	RCC->CFGR0 &= ~(0x1F<<11);
+
+	// Set up single conversion on chl 2
+	ADC1->RSQR1 = 0;
+	ADC1->RSQR2 = 0;
+
+	// turn on ADC and set rule group to sw trig
+	ADC1->CTLR2 |= ADC_ADON | ADC_EXTSEL;
+	
+	// Reset calibration
+	ADC1->CTLR2 |= ADC_RSTCAL;
+	while(ADC1->CTLR2 & ADC_RSTCAL);
+	
+	// Calibrate
+	ADC1->CTLR2 |= ADC_CAL;
+	while(ADC1->CTLR2 & ADC_CAL);
+}
+
+// Run from RAM to get even more stable timing.
+// This function call takes about 8.1uS to execute.
+uint32_t ReadTouchPin( GPIO_TypeDef * io, int portpin, int adcno ) __attribute__((noinline, section(".srodata")));
+uint32_t ReadTouchPin( GPIO_TypeDef * io, int portpin, int adcno )
+{
+	uint32_t ret = 0;
+
+	ADC1->RSQR3 = adcno;
+	ADC1->SAMPTR2 = ADC_SAMPLE_TIME<<(3*adcno);
+
+	uint32_t CFGBASE = io->CFGLR & (~(0xf<<(4*portpin)));
+	uint32_t CFGFLOAT = ((GPIO_CFGLR_IN_PUPD)<<(4*portpin)) | CFGBASE;
+	uint32_t CFGDRIVE = (GPIO_CFGLR_OUT_10Mhz_OD)<<(4*portpin) | CFGBASE;
+
+	int n;
+
+	// If we run multiple times with slightly different wait times, we can
+	// reduce the impact of the ADC's DNL.
+	for( n = MAX_SCALECHECK; n; n-- )
+	{
+		// Only lock IRQ for a very narrow window.
+		__disable_irq();
+
+		// Tricky - we start the ADC BEFORE we transition the pin.  By doing this
+		// We are catching it onthe slope much more effectively.
+		ADC1->CTLR2 = ADC_SWSTART | ADC_ADON | ADC_EXTSEL;
+		switch( n )
+		{
+			case 4:
+				asm volatile( "c.nop" );
+			case 3:
+				asm volatile( "c.nop" );
+			case 2:
+				asm volatile( "c.nop" );
+			case 1:
+				asm volatile( "c.nop" );
+		}
+		// Then we allow it to float.  By here, we typically have started sampling.
+		io->CFGLR = CFGFLOAT;
+		io->OUTDR = 1<<portpin;
+		__enable_irq();
+
+		while(!(ADC1->STATR & ADC_EOC));
+		io->CFGLR = CFGDRIVE;
+		io->OUTDR = 1<<(portpin+16);
+		ret += ADC1->RDATAR;
+	}
+
+	return ret;
+}
+
+int main()
+{
+	SystemInit();
+
+	printf("Capacitive Touch ADC example\n");
+	
+	// Enable GPIOD, C and ADC
+	RCC->APB2PCENR |= RCC_APB2Periph_GPIOA | RCC_APB2Periph_GPIOD | RCC_APB2Periph_GPIOC | RCC_APB2Periph_ADC1;
+
+	InitTouchADC();
+	
+	// should be ready for SW conversion now
+	while(1)
+	{
+		uint32_t start = SysTick->CNT;
+		uint32_t sum[8] = { 0 };
+
+		int j;
+
+		// Sampling all touch pads should take 3280 cycles, or about 68us.
+		// So it is possible to sample all channels at 14kHz
+		for( j = 0; j < 1; j++ )
+		{
+			sum[0] += ReadTouchPin( GPIOA, 2, 0 );
+			sum[1] += ReadTouchPin( GPIOA, 1, 1 );
+			sum[2] += ReadTouchPin( GPIOC, 4, 2 );
+			sum[3] += ReadTouchPin( GPIOD, 2, 3 );
+			sum[4] += ReadTouchPin( GPIOD, 3, 4 );
+			sum[5] += ReadTouchPin( GPIOD, 5, 5 );
+			sum[6] += ReadTouchPin( GPIOD, 6, 6 );
+			sum[7] += ReadTouchPin( GPIOD, 4, 7 );
+		}
+	
+		uint32_t end = SysTick->CNT;
+	
+		printf( "%d %d %d %d %d %d %d %d %d\n", (int)sum[0], (int)sum[1], (int)sum[2],
+			(int)sum[3], (int)sum[4], (int)sum[5], (int)sum[6], (int)sum[7], (int)(end-start) );
+	}
+}
+
+/*
+ * MIT License
+ * 
+ * Copyright (c) 2023 Valve Corporation
+ * 
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ * 
+ * The above copyright notice and this permission notice shall be included in all
+ * copies or substantial portions of the Software.
+ * 
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+ * SOFTWARE.
+ */
+
+

examples/cap_touch_adc/funconfig.h

+#ifndef _FUNCONFIG_H
+#define _FUNCONFIG_H
+
+#define CH32V003           1
+#define FUNCONF_SYSTICK_USE_HCLK 1
+
+#endif
+