1 files changed, 98 insertions, 0 deletions
diff --git a/fw/src/packet_interface.c b/fw/src/packet_interface.c
new file mode 100644
index 0000000..98a1ef2
--- /dev/null
+++ b/fw/src/packet_interface.c
@@ -0,0 +1,98 @@
+
+#include "packet_interface.h"
+#include "noise.h"
+#include "cobs.h"
+#include "tracing.h"
+
+#include <libopencm3/stm32/usart.h>
+#include <libopencm3/stm32/dma.h>
+#include <libopencm3/cm3/nvic.h>
+#include <libopencmsis/core_cm3.h>
+
+volatile struct {
+    struct dma_buf dma;
+    uint8_t data[256];
+} usart2_buf = { .dma = { .len = sizeof(usart2_buf.data) } };
+
+struct dma_usart_file usart2_out_s = {
+    .usart = USART2,
+    .baudrate = 115200,
+    .dma = DMA1,
+    .stream = 6,
+    .channel = 4,
+    .irqn = NVIC_DMA_IRQ(1, 6),
+    .buf = &usart2_buf.dma
+};
+struct dma_usart_file *usart2_out = &usart2_out_s;
+
+void dma1_stream6_isr(void) {
+    TRACING_SET(TR_HOST_IF_DMA_IRQ);
+    static unsigned int fifo_errors = 0; /* debug */
+    if (dma_get_interrupt_flag(usart2_out->dma, usart2_out->stream, DMA_FEIF)) {
+        /* Ignore FIFO errors as they're 100% non-critical for UART applications */
+        dma_clear_interrupt_flags(usart2_out->dma, usart2_out->stream, DMA_FEIF);
+        fifo_errors++;
+        TRACING_CLEAR(TR_HOST_IF_DMA_IRQ);
+        return;
+    }
+
+    /* Transfer complete interrupt */
+    dma_clear_interrupt_flags(usart2_out->dma, usart2_out->stream, DMA_TCIF);
+
+    if (usart2_out->buf->wr_pos != usart2_out->buf->xfr_end) /* buffer not empty */
+        schedule_dma(usart2_out);
+    TRACING_CLEAR(TR_HOST_IF_DMA_IRQ);
+}
+
+void usart2_isr(void) {
+    TRACING_SET(TR_HOST_IF_USART_IRQ);
+    static struct cobs_decode_state host_cobs_state = {0};
+    if (USART2_SR & USART_SR_ORE) { /* Overrun handling */
+        LOG_PRINTF("USART2 data register overrun\n");
+        /* Clear interrupt flag */
+        (void)USART2_DR; /* FIXME make sure this read is not optimized out */
+        host_packet_length = -1;
+        TRACING_CLEAR(TR_HOST_IF_USART_IRQ);
+        return;
+    }
+
+    uint8_t data = USART2_DR; /* This automatically acknowledges the IRQ */
+
+    if (host_packet_length) {
+        LOG_PRINTF("USART2 COBS buffer overrun\n");
+        host_packet_length = -1;
+        TRACING_CLEAR(TR_HOST_IF_USART_IRQ);
+        return;
+    }
+
+    ssize_t rv = cobs_decode_incremental(&host_cobs_state, (char *)host_packet_buf, sizeof(host_packet_buf), data);
+    if (rv == 0) {
+        /* good, empty frame */
+        LOG_PRINTF("Got empty frame from host\n");
+        host_packet_length = -1;
+    } else if (rv == -1) {
+        /* Decoding frame, wait for next byte */
+    } else if (rv == -2) {
+        LOG_PRINTF("Host interface COBS framing error\n");
+        host_packet_length = -1;
+    } else if (rv == -3) {
+        /* invalid empty frame */
+        LOG_PRINTF("Got double null byte from host\n");
+        host_packet_length = -1;
+    } else if (rv == -4) {
+        /* frame too large */
+        LOG_PRINTF("Got too large frame from host\n");
+        host_packet_length = -1;
+    } else if (rv > 0) {
+        /* Good, non-empty frame */
+        host_packet_length = rv;
+    }
+    TRACING_CLEAR(TR_HOST_IF_USART_IRQ);
+}
+
+void send_packet(struct dma_usart_file *f, const uint8_t *data, size_t len) {
+    /* ignore return value as putf is blocking and always succeeds */
+    (void)cobs_encode_incremental(f, putf, (char *)data, len);
+    flush(f);
+}
+