From b59a54e78d05a5deea9c60ee6416fcc94bca2d71 Mon Sep 17 00:00:00 2001
From: Robin Krens <robin@robinkrens.nl>
Date: Fri, 13 Sep 2019 18:14:03 +0700
Subject: [PATCH] mk450: code clean up and documentation

---
 drivers/mk450_joystick.c | 60 +++++++++++++++++++-----------------------------
 1 file changed, 24 insertions(+), 36 deletions(-)

diff --git a/drivers/mk450_joystick.c b/drivers/mk450_joystick.c
index a4c01d3..7ca3366 100644
--- a/drivers/mk450_joystick.c
+++ b/drivers/mk450_joystick.c
@@ -6,8 +6,18 @@
  * 
  * $DESCRIPTION$
  * Dual Axis XY Joystick controller
+ * Uses DMA to store converted input channels. The Analog to Digital
+ * converter (ADC1) is in scan mode and continuously monitors input
+ * channel 0 and 1. There is only one busy-wait for initial calibration
+ * of the ADC. The reference voltage here is 3300 mV. For 2500 mV (idle
+ * state of the joystick) this rougly translate to a value of 3100 
+ * (or 0xC1C) in the 12-bit data register (ADC1_DR). 
+ * Active and non-active (or left and right, up or down for the joystick)
+ * are 0x0 and 0xFFF respectively. 
  * 
  * $USAGE$
+ * Use getx and gety to get the current X and Y values of the joystick.
+ * How to use for games: TODO (description)
  *
  * */
 
@@ -29,13 +39,13 @@
 uint16_t xyvalues[2] = {0,0};
 
 
-/* Y return values is mV
- * ~2500 mv means y is idle state 
- * ~0 far left
- * ~5000 far right */
+/* Y return values is 
+ * ~0xC1C mv means y is idle state 
+ * ~0x0 far left
+ * ~0xFFF far right */
 uint16_t mk450_gety() {
 
-	int y = xyvalues[1];
+	int y = xyvalues[1]; 
 	return y;
 }
 
@@ -46,11 +56,13 @@ uint16_t mk450_getx() {
 	return x;
 }
 
+/* Initiate joystock module and DMA */
 void mk450_init() {
 
-	// clock prescaler
+	/* clock prescaler */
 	rsetbitsfrom(RCC_CFGR, 14, 0x3);
 
+	/* Peripherial init */
 	rsetbit(RCC_APB2ENR, 2); // enable GPIOA
 	rwrite(GPIOA_CRL, 0x44444400); // analog input on GPIOA0
 	rsetbit(RCC_APB2ENR, 9); // enable ADC1
@@ -58,26 +70,21 @@ void mk450_init() {
 	/* DMA init */
 	rsetbit(RCC_AHBENR, 0); // enable clock on DMA1
 	rwrite(DMA_CPAR1, (uint32_t) ADC1_DR);
-	rwrite(DMA_CMAR1, xyvalues);
+	rwrite(DMA_CMAR1, (uint32_t) xyvalues);
 	rwrite(DMA_CNDTR1, 2); // two values X and Y values
 	rsetbitsfrom(DMA_CCR1, 8, 0x1); // 16-bit
 	rsetbitsfrom(DMA_CCR1, 10, 0x1); // 16-bit
 	rsetbit(DMA_CCR1, 7); // memory increment mode
 	rsetbit(DMA_CCR1, 5); // circular mode
-
-	/* DMA Interrupt */
-	//ivt_set_gate(27, dma_interrupt, 0);
-	//rsetbit(NVIC_ISER0, 11);
-	//rsetbit(DMA_CCR1, 1);
-
 	rsetbit(DMA_CCR1, 0); // channel enable
 	
-	/* Scan mode for two input channels*/
+	/* Scan mode for two input channels */
 	rsetbitsfrom(ADC1_SQR1, 20, 0x1); // 2 channels
 	rsetbitsfrom(ADC1_SQR3, 0, 0x0); // ADC1_IN0
 	rsetbitsfrom(ADC1_SQR3, 5, 0x1); // ADC1_IN1
 	rsetbit(ADC1_CR1, 8); // scan mode
 	
+	/* Software start and channel config */
 	rsetbitsfrom(ADC1_CR2, 17, 0x7); // swstart config
 	rsetbit(ADC1_CR2, 20); // trigger enable
 	rsetbitsfrom(ADC1_SMPR2, 0, 0x7); // 237 cycles
@@ -86,30 +93,11 @@ void mk450_init() {
 
 	/* Calibrate */
 	rsetbit(ADC1_CR2, 2); // calibrate
-	_block(500);
-
-	/* Interrupt End of conversion (group!) */
-	//ivt_set_gate(34, eoc_interrupt, 0);
-	//rsetbit(NVIC_ISER0, 18);
-	//rsetbit(ADC1_CR1, 5);
-
+	_block(50);
+	
+	/* Wakeup TODO: check datasheet for double init */
 	rsetbit(ADC1_CR2, 8); // enable DMA	
 	rsetbit(ADC1_CR2, 0); // enable ADC
 	rsetbit(ADC1_CR2, 22); // swstart go!
 
 }
-
-/* End of conversion interrupt */
-void * eoc_interrupt() {
-	printf("SR1: %p\n", *ADC1_SR1);
-	printf("CR1: %p\n", *ADC1_CR1);
-	printf("CR2: %p\n", *ADC1_CR2);
-	printf("DR: %p\n", *ADC1_DR); // reading data registers clear interrupt flag
-}
-
-/* DMA interrupt */
-void * dma_interrupt() {
-	printf("DMA Interrupt!\n");
-	printf("Values: %x:%x\n", xyvalues[0], xyvalues[1] );
-	rsetbit(DMA_IFCR, 1);
-}
-- 
2.7.4