tim2_encoder example based on tim2_pwm_remap

Uses partially remapped pins to read a rotary encoder (or any quadrature
input) using pins that should be 5V tolerant

examples/tim2_encoder/Makefile

+all : flash
+
+TARGET:=tim2_encoder
+
+include ../../ch32v003fun/ch32v003fun.mk
+
+flash : cv_flash
+clean : cv_clean
+

examples/tim2_encoder/funconfig.h

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

examples/tim2_encoder/tim2_encoder.c

+/*
+ * Example for Timer 2 in "encoder" mode
+ * 07-01-2023 frosty adapted example from tim2_pwm_remap
+ *
+ * Usage: 
+ * Connect A/B pins of encoder to PC2/PC5
+ * Spin the encoder and see the count increase/decrease on the debug monitor
+ *
+ * Points of interest:
+ * 1. Port D pins and C0,C4, and C7 have a diode that clamps the pin to Vcc
+ * 	and are not 5V tolerant when Vcc is 3V3
+ * 2. Port C pins 1,2,3,5, and 6 are not clamped to Vcc and are should be
+ * 	5V tolerant.
+ * 2. Encoder mode uses CH1/CH2 so Timer2 must be used with a PARTIALREMAP1 so
+ * 	CH1/CH2 pins are on 5V tolerant pins.
+ * 3. If you don't require 5V tolerance you can use any of the REMAP options
+ *
+ * /
+
+
+Timer 2 pin mappings by AFIO->PCFR1
+	00	AFIO_PCFR1_TIM2_REMAP_NOREMAP
+		D4		T2CH1ETR
+		D3		T2CH2
+		C0		T2CH3
+		D7		T2CH4  --note: requires disabling nRST in opt
+	01	AFIO_PCFR1_TIM2_REMAP_PARTIALREMAP1
+		C5		T2CH1ETR_
+		C2		T2CH2_
+		D2		T2CH3_
+		C1		T2CH4_
+	10	AFIO_PCFR1_TIM2_REMAP_PARTIALREMAP2
+		C1		T2CH1ETR_
+		D3		T2CH2
+		C0		T2CH3
+		D7		T2CH4  --note: requires disabling nRST in opt
+	11	AFIO_PCFR1_TIM2_REMAP_FULLREMAP
+		C1		T2CH1ETR_
+		C7		T2CH2_
+		D6		T2CH3_
+		D5		T2CH4_
+*/
+
+#include "ch32v003fun.h"
+#include <stdio.h>
+
+/******************************************************************************************
+ * initialize TIM2 for PWM
+ ******************************************************************************************/
+void t2encoder_init( void )
+{
+	// Enable GPIOC, TIM2, and AFIO *very important!*
+	RCC->APB2PCENR |= RCC_APB2Periph_AFIO | RCC_APB2Periph_GPIOC;
+	RCC->APB1PCENR |= RCC_APB1Periph_TIM2;
+
+	AFIO->PCFR1 |= AFIO_PCFR1_TIM2_REMAP_PARTIALREMAP1; //set partial remap mode 1
+
+	// PC2 is T2CH1_, Input w/ Pullup/down
+	GPIOC->CFGLR &= ~(0xf<<(4*2)); //clear old values
+	GPIOC->CFGLR |= (GPIO_CNF_IN_PUPD)<<(4*2); //set new ones
+	//1 = pull-up, 0 = pull-down
+	GPIOC->OUTDR |= 1<<2;
+
+	// PC5 is T2CH2_, Input w/ Pullup/down
+	GPIOC->CFGLR &= ~(0xf<<(4*5)); //clear values
+	GPIOC->CFGLR |= (GPIO_CNF_IN_PUPD)<<(4*5); //set new ones
+	//1 = pull-up, 0 = pull-down
+	GPIOC->OUTDR |= 1<<5;
+	
+	// Reset TIM2 to init all regs
+	RCC->APB1PRSTR |= RCC_APB1Periph_TIM2;
+	RCC->APB1PRSTR &= ~RCC_APB1Periph_TIM2;
+	
+	// set TIM2 clock prescaler If you want to reduce the resolution of the encoder
+	//TIM2->PSC = 0x0000;
+
+	// set a automatic reload if you want the counter to wrap earlier than 0xffff
+	//TIM2->ATRLR = 0xffff;
+
+	// SMCFGR: set encoder mode SMS=011b
+	TIM2->SMCFGR |= TIM_EncoderMode_TI12;
+
+	// initialize timer
+	TIM2->SWEVGR |= TIM_UG;
+
+	// set count to about mid-scale to avoid wrap-around
+	TIM2->CNT = 0x8fff;
+
+	// Enable TIM2
+	TIM2->CTLR1 |= TIM_CEN;
+};
+
+/*****************************************************************************************
+ * entry
+ *****************************************************************************************/
+int main()
+{
+	SystemInit();
+
+
+	Delay_Ms( 100 );
+	t2encoder_init();
+
+	uint16_t initial_count = TIM2->CNT;
+	uint16_t last_count = TIM2->CNT;
+	while(1)
+	{
+		uint16_t count = TIM2->CNT;
+		if( count != last_count) {
+			printf("Position relative=%ld absolute=%u delta=%ld\n",(int32_t)count - initial_count, count, (int32_t)count-last_count);
+			last_count = count;
+		}
+		Delay_Ms(50);
+	}
+}