Add basic 9-channel BCM output

build-number.txt

@@ -1 +1 @@
-0
+80

src/led.c

@@ -0,0 +1,170 @@
+#include "led.h"
+#include "stm32f030x6.h"
+
+#define LED_ODR_MASK            ((1 << PIN_LED_R_0) | (1 << PIN_LED_G_0) \
+                                | (1 << PIN_LED_B_0) | (1 << PIN_LED_R_1) \
+                                | (1 << PIN_LED_G_1) | (1 << PIN_LED_B_1) \
+                                | (1 << PIN_LED_R_2) | (1 << PIN_LED_G_2) \
+                                | (1 << PIN_LED_B_2))
+
+#define LED_MODER_MASK          ((3 << PIN_LED_R_0 * 2) | (3 << PIN_LED_G_0 * 2) \
+                                | (3 << PIN_LED_B_0 * 2) | (3 << PIN_LED_R_1 * 2) \
+                                | (3 << PIN_LED_G_1 * 2) | (3 << PIN_LED_B_1 * 2) \
+                                | (3 << PIN_LED_R_2 * 2) | (3 << PIN_LED_G_2 * 2) \
+                                | (3 << PIN_LED_B_2 * 2))
+
+#define LED_MODER               ((1 << PIN_LED_R_0 * 2) | (1 << PIN_LED_G_0 * 2) \
+                                | (1 << PIN_LED_B_0 * 2) | (1 << PIN_LED_R_1 * 2) \
+                                | (1 << PIN_LED_G_1 * 2) | (1 << PIN_LED_B_1 * 2) \
+                                | (1 << PIN_LED_R_2 * 2) | (1 << PIN_LED_G_2 * 2) \
+                                | (1 << PIN_LED_B_2 * 2))
+
+uint8_t LED_Data[LED_COUNT] = {0, 63, 200, 255};
+
+// TIM3 is clocked by APB1 and thus receives only half the system clock. The 4
+// LSBs have bit lengths 2, 4, 8, and 16 cycles and are generated blocking from
+// an inline assembly block and are thus not in this table.
+static const uint16_t LED_BitLengths[LED_BITS - 4] =
+{
+    16, 32, 64, 128, 256, 512, 1024, 2048
+};
+
+static uint16_t LED_DMABuffer[LED_BITS + 1];
+
+static void LED_RefreshDMABuffer(void)
+{
+    for(int i = 0; i < LED_COUNT; i++)
+    {
+        uint16_t gamma_corrected = (uint16_t)LED_Data[i] * LED_Data[i];
+        gamma_corrected >>= 16 - LED_BITS;
+
+        for(int j = 0; j < LED_BITS; j++)
+        {
+            if(gamma_corrected & (1 << j))
+            {
+                LED_DMABuffer[j] |= 1 << i;
+            }
+            else
+            {
+                LED_DMABuffer[j] &= ~(1 << i);
+            }
+        }
+    }
+    // Data to reset outputs after all data bits are sent
+    LED_DMABuffer[LED_BITS] = 0x0000;
+}
+
+static void LED_StartBCM(void)
+{
+    // Reset DMA and timer
+    TIM3->CR1 = 0x0000;
+    TIM3->DIER = 0x0000;
+    TIM3->CNT = 0;
+    DMA1_Channel3->CCR = 0x0000;
+    DMA1_Channel4->CCR = 0x0000;
+
+    TIM3->ARR = 1; // Delay before everything starts with the first DMA request
+    TIM3->CR1 = TIM_CR1_ARPE;
+    // Since ARPE is set, this write goes to ARR's shadow register
+    TIM3->ARR = LED_BitLengths[0];
+    TIM3->DIER = TIM_DIER_UDE | TIM_DIER_CC1DE;
+
+    // DMA channel 3: Output data to port a on TIM3 update
+    DMA1_Channel3->CMAR = (uint32_t)&(LED_DMABuffer[4]);
+    // One transfer for each bit plus one to set the outputs to zero again.
+    // The first 4 are sent out with assembly before the first DMA transfer.
+    DMA1_Channel3->CNDTR = LED_BITS + 1 - 4;
+    // Highest priority, 16 bits, increment memory, memory to peripheral
+    DMA1_Channel3->CCR = DMA_CCR_PL | DMA_CCR_MSIZE_0 | DMA_CCR_PSIZE_0
+        | DMA_CCR_MINC | DMA_CCR_DIR | DMA_CCR_EN | DMA_CCR_TCIE;
+
+    // DMA channel 3: Output data to port a on TIM3 update
+    // The bit lengths table is offset because the first value is already in
+    // the timer's ARR shadow register.
+    DMA1_Channel4->CMAR = (uint32_t)&(LED_BitLengths[1]);
+    // The first four bits are sent out with the assembly code below, so only
+    // LED_BITS - 5 bit lengths are needed.
+    DMA1_Channel4->CNDTR = LED_BITS - 1 - 4;
+    // 16 bits, memory increment mode, memory to peripheral
+    DMA1_Channel4->CCR = DMA_CCR_MSIZE_0 | DMA_CCR_PSIZE_0 | DMA_CCR_MINC
+        | DMA_CCR_DIR | DMA_CCR_EN;
+
+    // Send the 4 LSBs, set to zero at the end (so the timing is independent
+    // from the delay intrudoced by the DMA)
+    __asm__ volatile(".syntax unified\n"
+            "str %[d0], [%[odr]];"
+            "str %[d1], [%[odr]];"
+            "nop;"
+            "nop;"
+            "str %[d2], [%[odr]];"
+            "nop;"
+            "nop;"
+            "nop;"
+            "nop;"
+            "nop;"
+            "nop;"
+            "str %[d3], [%[odr]];"
+            "nop;"
+            "nop;"
+            "nop;"
+            "nop;"
+            "nop;"
+            "nop;"
+            "nop;"
+            "nop;"
+            "nop;"
+            "nop;"
+            "nop;"
+            "nop;"
+            "nop;"
+            "nop;"
+            "str %[zero], [%[odr]];"
+            :
+            : [odr] "l" ((uint32_t)&(GPIOA->ODR)),
+              [d0] "r" (LED_DMABuffer[0]),
+              [d1] "r" (LED_DMABuffer[1]),
+              [d2] "r" (LED_DMABuffer[2]),
+              [d3] "r" (LED_DMABuffer[3]),
+              [zero] "r" (0)
+            :);
+
+    // Enable TIM3 for the rest of the bits
+    TIM3->CR1 = TIM_CR1_ARPE | TIM_CR1_CEN;
+}
+
+void LED_Init(void)
+{
+    RCC->AHBENR |= RCC_AHBENR_GPIOAEN;
+    RCC->AHBENR |= RCC_AHBENR_DMA1EN;
+    RCC->APB1ENR |= RCC_APB1ENR_TIM3EN;
+
+    GPIOA->ODR &= ~LED_ODR_MASK;
+    GPIOA->MODER = (GPIOA->MODER & ~LED_MODER_MASK) | LED_MODER;
+
+    TIM3->CR1 = 0x0000;
+    TIM3->PSC = 0;
+    // CH1 will be used for DMA requests updating ARR
+    TIM3->CCMR1 = TIM_CCMR1_OC1M_2 | TIM_CCMR1_OC1M_1;
+    TIM3->CCER = TIM_CCER_CC1E;
+    TIM3->CCR1 = 1;
+
+    // DMA channel 3: Output data to port a on TIM3 update
+    DMA1_Channel3->CPAR = (uint32_t)&(GPIOA->ODR);
+
+    // DMA channel 4: Update TIM3 ARR on TIM3 CH1 (which is set to 0)
+    DMA1_Channel4->CPAR = (uint32_t)&(TIM3->ARR);
+
+    NVIC_EnableIRQ(DMA1_Channel2_3_IRQn);
+
+    LED_RefreshDMABuffer();
+    LED_StartBCM();
+}
+
+void DMA1_Channel2_3_IRQHandler(void)
+{
+    // Interrupt when all bits have been sent
+    DMA1->IFCR = DMA_IFCR_CTCIF3;
+
+    // Start sending bits out again
+    LED_StartBCM();
+}

src/led.h

@@ -0,0 +1,10 @@
+#pragma once
+
+#include "stm32f030x6.h"
+#include "pinning.h"
+
+#define LED_BITS                12
+#define LED_COUNT               9
+
+void LED_Init(void);
+

src/main.c

@@ -2,6 +2,8 @@
 
 int main(void)
 {
+    LED_Init();
+
     while(1)
     {
     }

src/main.h

@@ -2,6 +2,7 @@
 
 #include "stm32f030x6.h"
 #include "buildid.h"
+#include "led.h"
 
 int main(void);
 

src/pinning.h

@@ -0,0 +1,12 @@
+#pragma once
+
+// Port A
+#define PIN_LED_R_0             0
+#define PIN_LED_G_0             1
+#define PIN_LED_B_0             2
+#define PIN_LED_R_1             3
+#define PIN_LED_G_1             4
+#define PIN_LED_B_1             5
+#define PIN_LED_R_2             6
+#define PIN_LED_G_2             7
+#define PIN_LED_B_2             9