Add LED matrix control (12×8)

build-number.txt

@@ -1 +1 @@
-84
+129

src/led.c

@@ -22,7 +22,7 @@
                                 | (1 << PIN_LED_B_2 * 2) | (1 << PIN_LED_R_3 * 2) \
                                 | (1 << PIN_LED_G_3 * 2) | (1 << PIN_LED_B_3 * 2))
 
-uint8_t LED_Data[LED_COUNT] = {0, 63, 200, 255};
+uint8_t LED_Data[LED_ROWS][LED_COLUMNS] = {{0}};
 
 // 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
@@ -32,7 +32,7 @@ static const uint16_t LED_BitLengths[LED_BITS - 4] =
     16, 32, 64, 128, 256, 512, 1024, 2048
 };
 
-static const int LED_Pins[LED_COUNT] =
+static const int LED_Pins[LED_COLUMNS] =
 {
     PIN_LED_R_0, PIN_LED_G_0, PIN_LED_B_0,
     PIN_LED_R_1, PIN_LED_G_1, PIN_LED_B_1,
@@ -40,32 +40,37 @@ static const int LED_Pins[LED_COUNT] =
     PIN_LED_R_3, PIN_LED_G_3, PIN_LED_B_3
 };
 
-static uint16_t LED_DMABuffer[LED_BITS + 1];
+static uint16_t LED_DMABuffer[LED_ROWS * (LED_BITS + 1)];
 
 static void LED_RefreshDMABuffer(void)
 {
-    for(int i = 0; i < LED_COUNT; i++)
+    for(int r = 0; r < LED_ROWS; r++)
     {
-        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++)
+        for(int i = 0; i < LED_COLUMNS; i++)
         {
-            if(gamma_corrected & (1 << j))
+            uint16_t gamma_corrected = (uint16_t)LED_Data[r][i];
+            gamma_corrected *= gamma_corrected;
+            gamma_corrected >>= 16 - LED_BITS;
+
+            for(int j = 0; j < LED_BITS; j++)
             {
-                LED_DMABuffer[j] &= ~(1 << LED_Pins[i]);
-            }
-            else
-            {
-                LED_DMABuffer[j] |= 1 << LED_Pins[i];
+                if(gamma_corrected & (1 << j))
+                {
+                    LED_DMABuffer[r * (LED_BITS + 1) + j] &=
+                        ~(1 << LED_Pins[i]);
+                }
+                else
+                {
+                    LED_DMABuffer[r * (LED_BITS + 1) + j] |= 1 << LED_Pins[i];
+                }
             }
         }
+        // Data to reset outputs after all data bits are sent
+        LED_DMABuffer[r * (LED_BITS + 1) + LED_BITS] = LED_ODR_MASK;
     }
-    // Data to reset outputs after all data bits are sent
-    LED_DMABuffer[LED_BITS] = 0x0000;
 }
 
-static void LED_StartBCM(void)
+static void LED_StartBCM(int row)
 {
     // Reset DMA and timer
     TIM3->CR1 = 0x0000;
@@ -81,7 +86,7 @@ static void LED_StartBCM(void)
     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]);
+    DMA1_Channel3->CMAR = (uint32_t)&(LED_DMABuffer[row * (LED_BITS + 1) + 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;
@@ -101,7 +106,7 @@ static void LED_StartBCM(void)
         | 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)
+    // from the delay introduced by the DMA)
     __asm__ volatile(".syntax unified\n"
             "str %[d0], [%[odr]];"
             "str %[d1], [%[odr]];"
@@ -132,10 +137,10 @@ static void LED_StartBCM(void)
             "str %[off], [%[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]),
+              [d0] "r" (LED_DMABuffer[row * (LED_BITS + 1) + 0]),
+              [d1] "r" (LED_DMABuffer[row * (LED_BITS + 1) + 1]),
+              [d2] "r" (LED_DMABuffer[row * (LED_BITS + 1) + 2]),
+              [d3] "r" (LED_DMABuffer[row * (LED_BITS + 1) + 3]),
               [off] "r" (LED_ODR_MASK)
             :);
 
@@ -143,13 +148,38 @@ static void LED_StartBCM(void)
     TIM3->CR1 = TIM_CR1_ARPE | TIM_CR1_CEN;
 }
 
+static inline void LED_PulseRowClock(void)
+{
+    __asm__ volatile("nop");
+    GPIOF->BSRR = (1 << PIN_ROW_SCK);
+    __asm__ volatile("nop");
+    GPIOF->BRR = (1 << PIN_ROW_SCK);
+}
+
 void LED_Init(void)
 {
     RCC->AHBENR |= RCC_AHBENR_GPIOAEN;
+    RCC->AHBENR |= RCC_AHBENR_GPIOFEN;
     RCC->AHBENR |= RCC_AHBENR_DMA1EN;
     RCC->APB1ENR |= RCC_APB1ENR_TIM3EN;
 
+    GPIOF->ODR &= ~(1 << PIN_ROW_SCK) & ~(1 << PIN_ROW_DATA);
+    GPIOF->MODER = (GPIOF->MODER
+        & ~(0x3 << PIN_ROW_SCK * 2) & ~(0x3 << PIN_ROW_DATA * 2))
+        | (0x1 << PIN_ROW_SCK * 2) | (0x1 << PIN_ROW_DATA * 2);
+
+    // Reset the shift register. Since RCK and SCK are shorted together, one
+    // additional clock cycle is needed.
+    GPIOF->BSRR = (1 << PIN_ROW_DATA);
+    for(int i = 0; i < LED_ROWS + 1; i++)
+    {
+        LED_PulseRowClock();
+    }
+    // All shift register outputs are now '1'. Because the rows are driven with
+    // external transistors, this means all rows are off.
+
     GPIOA->ODR |= LED_ODR_MASK;
+    GPIOA->PUPDR &= ~LED_MODER_MASK;
     GPIOA->OTYPER |= LED_ODR_MASK;
     GPIOA->MODER = (GPIOA->MODER & ~LED_MODER_MASK) | LED_MODER;
 
@@ -169,7 +199,7 @@ void LED_Init(void)
     NVIC_EnableIRQ(DMA1_Channel2_3_IRQn);
 
     LED_RefreshDMABuffer();
-    LED_StartBCM();
+    LED_StartBCM(0);
 }
 
 void DMA1_Channel2_3_IRQHandler(void)
@@ -177,6 +207,23 @@ 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();
+    static int current_row = 0;
+    current_row++;
+    if(current_row >= LED_ROWS)
+    {
+        GPIOF->BRR = 1 << PIN_ROW_DATA;
+        current_row = 0;
+        LED_PulseRowClock();
+        GPIOF->BSRR = 1 << PIN_ROW_DATA;
+    }
+    else
+    {
+        LED_PulseRowClock();
+    }
+
+    // Start sending bits out again. The row offset caused by the shift
+    // register "lagging" one clock cycle behind because RCK and SCK are
+    // connected to the same signal doesn't matter here: we're not paying much
+    // attention to which rows are which anyway.
+    LED_StartBCM(current_row);
 }

src/led.h

@@ -4,7 +4,8 @@
 #include "pinning.h"
 
 #define LED_BITS                12
-#define LED_COUNT               12
+#define LED_ROWS                8   // Rows are driven by a shift register
+#define LED_COLUMNS             12  // Columns are driven by the MCU directly
 
 void LED_Init(void);
 

src/main.c

@@ -2,6 +2,12 @@
 
 int main(void)
 {
+    // Delay a bit to make programming easier
+    for(int i = 0; i < 30000; i++)
+    {
+        __asm__ volatile("nop");
+    }
+
     LED_Init();
 
     while(1)

src/pinning.h

@@ -13,3 +13,7 @@
 #define PIN_LED_R_3             10
 #define PIN_LED_G_3             13
 #define PIN_LED_B_3             14
+
+// Port F
+#define PIN_ROW_DATA            0   // Shift register data in
+#define PIN_ROW_SCK             1   // Shift register clock