DMA checkpoint; dma_attach_interrupt() is broken.

Simple USART receiver to SRAM buffer demo partially working.
Interrupting when buffer is full fails mysteriously.  GDB thinks
we ended up in an STM32 reserved exception.

1 files changed, 127 insertions, 0 deletions

diff --git a/examples/test-usart-dma.cpp b/examples/test-usart-dma.cpp
new file mode 100644
index 0000000..b9c03f1
--- /dev/null
+++ b/examples/test-usart-dma.cpp
@@ -0,0 +1,127 @@
+/**
+ * @file test-usart-dma.cpp
+ * @author Marti Bolivar <mbolivar@leaflabs.com>
+ *
+ * Simple test of DMA used with a USART receiver.
+ *
+ * Configures a USART receiver for use with DMA.  Received bytes are
+ * placed into a buffer, with an interrupt firing when the buffer is
+ * full.  At that point, the USART transmitter will print the contents
+ * of the byte buffer.  The buffer is continually filled and refilled
+ * in this manner.
+ *
+ * This example isn't very robust; don't use it in production.  In
+ * particular, since the buffer keeps filling (DMA_CIRC_MODE is set),
+ * if you keep typing after filling the buffer, you'll overwrite
+ * earlier bytes; this may happen before those earlier bytes are done
+ * printing.
+ *
+ * This code is released into the public domain.
+ */
+
+#include "dma.h"
+#include "usart.h"
+#include "gpio.h"
+
+#include "wirish.h"
+
+#define BAUD 9600
+
+#define USART USART2
+#define USART_HWSER Serial2
+#define USART_DMA_DEV DMA1
+#define USART_RX_DMA_CHANNEL DMA_CH6
+#define USART_TX BOARD_USART2_TX_PIN
+#define USART_RX BOARD_USART2_RX_PIN
+
+#define BUF_SIZE 8
+uint8 rx_buf[BUF_SIZE];
+
+dma_irq_cause irq_cause;
+
+__io uint32 irq_fired = 0;
+
+void init_usart(void);
+void init_dma_xfer(void);
+void rx_dma_irq(void);
+
+void setup(void) {
+    pinMode(BOARD_LED_PIN, OUTPUT);
+
+    init_dma_xfer();
+    init_usart();
+}
+
+void loop(void) {
+    toggleLED();
+    delay(100);
+
+    dma_channel_reg_map *ch_regs = dma_channel_regs(USART_DMA_DEV,
+                                                    USART_RX_DMA_CHANNEL);
+    if (irq_fired) {
+        USART_HWSER.println("** IRQ **");
+        while (true)
+            ;
+    }
+    USART_HWSER.print("[");
+    USART_HWSER.print(millis());
+    USART_HWSER.print("]\tISR bits: 0x");
+    uint8 isr_bits = dma_get_isr_bits(USART_DMA_DEV, USART_RX_DMA_CHANNEL);
+    USART_HWSER.print((int32)isr_bits, HEX);
+    USART_HWSER.print("\tCCR: 0x");
+    USART_HWSER.print((int64)ch_regs->CCR, HEX);
+    USART_HWSER.print("\tCNDTR: 0x");
+    USART_HWSER.print((int64)ch_regs->CNDTR, HEX);
+    USART_HWSER.print("\tBuffer contents: ");
+     for (int i = 0; i < BUF_SIZE; i++) {
+        USART_HWSER.print('\'');
+        USART_HWSER.print(rx_buf[i]);
+        USART_HWSER.print('\'');
+        if (i < BUF_SIZE - 1) USART_HWSER.print(", ");
+    }
+    USART_HWSER.println();
+    if (isr_bits == 0x7) {
+        USART_HWSER.println("** Clearing ISR bits.");
+        dma_clear_isr_bits(USART_DMA_DEV, USART_RX_DMA_CHANNEL);
+    }
+
+    irq_fired = 0;
+}
+
+/* Configure USART receiver for use with DMA */
+void init_usart(void) {
+    USART_HWSER.begin(BAUD);
+    USART->regs->CR3 = USART_CR3_DMAR;
+}
+
+/* Configure DMA transmission */
+void init_dma_xfer(void) {
+    dma_init(USART_DMA_DEV);
+    dma_setup_transfer(USART_DMA_DEV, USART_RX_DMA_CHANNEL,
+                       &USART->regs->DR, DMA_SIZE_8BITS,
+                       rx_buf,           DMA_SIZE_8BITS,
+                       (DMA_MINC_MODE | DMA_CIRC_MODE | DMA_TRNS_CMPLT
+                        ));
+    dma_set_num_transfers(USART_DMA_DEV, USART_RX_DMA_CHANNEL, BUF_SIZE);
+    // Currently not working:
+    // dma_attach_interrupt(USART_DMA_DEV, USART_RX_DMA_CHANNEL, rx_dma_irq);
+    dma_enable(USART_DMA_DEV, USART_RX_DMA_CHANNEL);
+}
+
+void rx_dma_irq(void) {
+}
+
+// Force init to be called *first*, i.e. before static object allocation.
+// Otherwise, statically allocated objects that need libmaple may fail.
+__attribute__((constructor)) void premain() {
+    init();
+}
+
+int main(void) {
+    setup();
+
+    while (true) {
+        loop();
+    }
+    return 0;
+}