From 369c0909555371866df5fcc3d267927aee5aafa6 Mon Sep 17 00:00:00 2001
From: jaseg <git@jaseg.net>
Date: Mon, 14 Aug 2017 12:51:49 +0200
Subject: Multiplexing is working

---
 fw/main.c | 213 ++++++++++++++++++++++++++++++++++++++++++++------------------
 1 file changed, 152 insertions(+), 61 deletions(-)

(limited to 'fw/main.c')

diff --git a/fw/main.c b/fw/main.c
index 73e7280..7153d59 100644
--- a/fw/main.c
+++ b/fw/main.c
@@ -1,18 +1,26 @@
 
+
+#pragma GCC diagnostic push
+#pragma GCC diagnostic ignored "-Wstrict-aliasing"
 #include <stm32f0xx.h>
-#include <stdint.h>
-#include <system_stm32f0xx.h>
 #include <stm32f0xx_ll_utils.h>
 #include <stm32f0xx_ll_spi.h>
+#pragma GCC diagnostic pop
+
+#include <system_stm32f0xx.h>
+
+#include <stdint.h>
 #include <string.h>
 #include <unistd.h>
 /* 
  * Part number: STM32F030F4C6
  */
 
-void tick(void) {
-    for(int i=0; i<50; i++)
-        __asm__("nop");
+/* Wait for about 0.2us */
+static void tick(void) {
+                    /* 1 */         /* 2 */         /* 3 */         /* 4 */         /* 5 */
+    /*  5 */ __asm__("nop"); __asm__("nop"); __asm__("nop"); __asm__("nop"); __asm__("nop");
+    /* 10 */ __asm__("nop"); __asm__("nop"); __asm__("nop"); __asm__("nop"); __asm__("nop");
 }
 
 void spi_send(int data) {
@@ -32,18 +40,117 @@ void strobe_leds(void) {
     GPIOA->BSRR = GPIO_BSRR_BR_9;
 }
 
-#define SR_COMM      0x0002
-#define SR_ERROR     0x0004
-#define SR_ID        0x0008
+static volatile unsigned int sys_time = 0;
+
+enum Segment { SegA, SegB, SegC, SegD, SegE, SegF, SegG, SegDP, nsegments };
+enum {
+    nrows = 4,
+    ncols = 8,
+    nbits = 10,
+};
+enum {
+    frame_size_words = nrows*ncols*nsegments/32,
+};
+struct framebuf {
+    /* Multiplexing order: first Digits, then Time/bits, last Segments */
+    uint32_t data[nbits*frame_size_words];
+    int brightness; /* 0 or 1; controls global brighntess control */
+};
+
+struct framebuf fb[2] = {0};
+struct framebuf *read_fb=fb+0, *write_fb=fb+1;
+volatile int led_state = 0;
+volatile enum { FB_WRITE, FB_UPDATE } fb_op;
+
+#define LED_COMM     0x0001
+#define LED_ERROR    0x0002
+#define LED_ID       0x0004
 #define SR_ILED_HIGH 0x0080
 #define SR_ILED_LOW  0x0040
+
+void shift_aux(int global_current, int leds, int active_segment) {
+    spi_send(
+              (global_current ? SR_ILED_HIGH : SR_ILED_LOW)
+            | (leds<<1)
+            | (0xff00 ^ (0x100<<active_segment)));
+    strobe_aux();
+}
+
+static volatile int frame_duration;
+/* returns new bit time in cycles */
+int shift_data() {
+    static int active_segment = 0;
+    static unsigned int active_bit = 0;
+    static int last_frame_sys_time;
+
+    /* Note: On boot, multiplexing will start with bit 1 due to the next few lines. This is perfectly ok. */
+    active_bit++;
+    if (active_bit == nbits) {
+        active_bit = 0;
+
+        active_segment++;
+        if (active_segment == nsegments) {
+            active_segment = 0;
+
+            int time = sys_time;
+            frame_duration = time - last_frame_sys_time;
+            last_frame_sys_time = sys_time;
+            if (fb_op == FB_UPDATE) {
+                struct framebuf *tmp = read_fb;
+                read_fb = write_fb;
+                write_fb = tmp;
+                fb_op = FB_WRITE;
+            }
+        }
+
+        shift_aux(read_fb->brightness, led_state, active_segment);
+    }
+
+    uint32_t current_word = read_fb->data[active_bit*frame_size_words + active_segment];
+    spi_send(current_word&0xffff);
+    spi_send(current_word>>16);
+    strobe_leds();
+
+    return 1<<active_bit;
+}
+
+void cfg_timer3() {
+    TIM3->CCMR1 = 6<<TIM_CCMR1_OC1M_Pos; /* PWM Mode 1 */
+    TIM3->CCER  = TIM_CCER_CC1E | TIM_CCER_CC1P; /* Inverting output */
+    TIM3->DIER  = TIM_DIER_CC1IE;
+    TIM3->CCR1  = 1000; /* Schedule first interrupt */
+    TIM3->PSC   = SystemCoreClock/5000000 * 2; /* 0.40us/tick */
+    TIM3->ARR   = 0xffff;
+    TIM3->EGR  |= TIM_EGR_UG;
+    TIM3->CR1   = TIM_CR1_ARPE;
+    TIM3->CR1  |= TIM_CR1_CEN;
+}
+
+TIM_TypeDef *tim3 = TIM3;
+
+void TIM3_IRQHandler() {
+    //TIM3->CR1 &= ~TIM_CR1_CEN_Msk;
+
+    static int last_ivl;
+    last_ivl = TIM3->CNT;
+    /* This takes about 10us */
+    int period = shift_data();
+    static int ivl;
+    ivl = TIM3->CNT - last_ivl;
+    TIM3->CCR1 = period;
+    TIM3->CNT = 0xffff; /* To not enable OC1 right away */
+
+    TIM3->SR &= ~TIM_SR_CC1IF_Msk;
+    //TIM3->CR1 |= TIM_CR1_CEN;
+}
+
 int main(void) {
     RCC->CR |= RCC_CR_HSEON;
     while (!(RCC->CR&RCC_CR_HSERDY));
-    RCC->CFGR &= ~RCC_CFGR_PLLMUL_Msk & ~RCC_CFGR_SW_Msk;
-    RCC->CFGR |= (2<<RCC_CFGR_PLLMUL_Pos) | RCC_CFGR_PLLSRC_HSE_PREDIV; /* PLL x4 */
+    RCC->CFGR &= ~RCC_CFGR_PLLMUL_Msk & ~RCC_CFGR_SW_Msk & ~RCC_CFGR_PPRE_Msk & ~RCC_CFGR_HPRE_Msk;
+    RCC->CFGR |= (1<<RCC_CFGR_PLLMUL_Pos) | RCC_CFGR_PLLSRC_HSE_PREDIV; /* PLL x4 -> 50.0MHz */
     RCC->CFGR2 &= ~RCC_CFGR2_PREDIV_Msk;
-    RCC->CFGR2 |= RCC_CFGR2_PREDIV_DIV2;
+    RCC->CFGR2 |= RCC_CFGR2_PREDIV_DIV2; /* prediv :2 -> 12.5MHz */
     RCC->CR |= RCC_CR_PLLON;
     while (!(RCC->CR&RCC_CR_PLLRDY));
     RCC->CFGR |= (2<<RCC_CFGR_SW_Pos);
@@ -53,10 +160,11 @@ int main(void) {
 
     RCC->AHBENR  |= RCC_AHBENR_GPIOAEN;
     RCC->APB2ENR |= RCC_APB2ENR_SPI1EN;
+    RCC->APB1ENR |= RCC_APB1ENR_TIM3EN;
 
     GPIOA->MODER |=
           (2<<GPIO_MODER_MODER5_Pos)  /* PA5  - SCLK */
-        | (1<<GPIO_MODER_MODER6_Pos)  /* PA6  - LED !OE */
+        | (2<<GPIO_MODER_MODER6_Pos)  /* PA6  - LED !OE */
         | (2<<GPIO_MODER_MODER7_Pos)  /* PA7  - MOSI */
         | (1<<GPIO_MODER_MODER9_Pos)  /* PA9  - LED strobe */
         | (1<<GPIO_MODER_MODER10_Pos);/* PA10 - Auxiliary strobe */
@@ -71,6 +179,7 @@ int main(void) {
 
     GPIOA->AFR[0] |=
           (0<<GPIO_AFRL_AFRL5_Pos)   /* SPI1_SCK  */
+        | (1<<GPIO_AFRL_AFRL6_Pos)   /* TIM3_CH1  */
         | (0<<GPIO_AFRL_AFRL7_Pos);  /* SPI1_MOSI */
 
     /* Configure SPI controller */
@@ -79,60 +188,41 @@ int main(void) {
     SPI1->CR2 &= ~SPI_CR2_DS_Msk;
     SPI1->CR2 |= LL_SPI_DATAWIDTH_16BIT;
     /* FIXME maybe try w/o BIDI */
+    /* Baud rate PCLK/2 -> 25MHz */
     SPI1->CR1 = SPI_CR1_BIDIMODE | SPI_CR1_BIDIOE | SPI_CR1_SSM | SPI_CR1_SSI | SPI_CR1_SPE | (0<<SPI_CR1_BR_Pos) | SPI_CR1_MSTR | SPI_CR1_CPOL | SPI_CR1_CPHA;
 
-    int val = 0xffff;
-    int aval = 0x0000;
-    GPIOA->BSRR = GPIO_BSRR_BR_6; /* OE */
-    int j = 0;
-    int ctr = 0;
-    int q = 0;
-    int bval = 0x400;
+    read_fb->brightness = 1;
+    for (int i=0; i<sizeof(read_fb->data)/sizeof(uint32_t); i++) {
+        read_fb->data[i] = 0xffffffff;
+    }
+    cfg_timer3();
+
+    NVIC_EnableIRQ(TIM3_IRQn);
+    NVIC_SetPriority(TIM3_IRQn, 2);
+
+    SysTick_Config(SystemCoreClock/1000); /* 1ms interval */
+
     while (42) {
-        for (int i=0; i<8; i++) {
-            spi_send(1<<(ctr&3));
-            spi_send(1<<((ctr>>1)&3));
-            strobe_leds();
-            //spi_send(0x0200 | bval | (0xff^(1<<i)));
-            //spi_send((0xff^(1<<i))<<8);
-            //spi_send(SR_COMM | SR_ILED_HIGH | 0xff);
-            //spi_send(0x00ff ^ (1<<ctr) | (0x100<<ctr));
-            spi_send(bval | (0xff00 ^ (0x100<<i)));
-            strobe_aux();
-            for(int i=0; i<10; i++)
-                tick();
-            j++;
-            if (j == 1000) {
-                j = 0;
-                ctr++;
-                if (ctr == 8) {
-                    ctr = 0;
-                    q++;
-                    if (q == 6)
-                        q = 0;
-                }
-                switch (q) {
-                    case 0:
-                        bval = SR_COMM  | SR_ILED_LOW;
-                        break;
-                    case 1:
-                        bval = SR_ID    | SR_ILED_LOW;
-                        break;
-                    case 2:
-                        bval = SR_ERROR | SR_ILED_LOW;
-                        break;
-                    case 3:
-                        bval = SR_COMM  | SR_ILED_HIGH;
-                        break;
-                    case 4:
-                        bval = SR_ID    | SR_ILED_HIGH;
-                        break;
-                    case 5:
-                        bval = SR_ERROR | SR_ILED_HIGH;
-                        break;
-                }
+        led_state = (sys_time>>8)&7;
+
+        int ctr = sys_time>>2;
+        for (int bit=0, bmask=1; bit<nbits; bit++, bmask<<=1) {
+
+            int data = 0;
+            for (uint32_t ibit = 1, j=0; ibit; ibit<<=1, j++) {
+                int _100 = (1<<nbits);
+                int _1ff = (2*_100-1);
+                int val = (ctr + (j<<(nbits-5))) & _1ff;
+                val = val&_100 ? _1ff-val : val;
+                data |= val&bmask ? ibit : 0;
             }
+
+            for (int seg=0; seg<frame_size_words; seg++)
+                write_fb->data[bit*frame_size_words + seg] = data;
         }
+        fb_op = FB_UPDATE;
+        while (fb_op == FB_UPDATE)
+            ;
     }
 }
 
@@ -151,5 +241,6 @@ void PendSV_Handler(void) {
 }
 
 void SysTick_Handler(void) {
+    sys_time++;
 }
 
-- 
cgit