1 files changed, 46 insertions, 0 deletions
diff --git a/gm_platform/fw/packet_interface.c b/gm_platform/fw/packet_interface.c
new file mode 100644
index 0000000..099993b
--- /dev/null
+++ b/gm_platform/fw/packet_interface.c
@@ -0,0 +1,46 @@
+
+#include "packet_interface.h"
+#include "cobs.h"
+
+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 == -2) {
+        LOG_PRINTF("Host interface COBS packet too large\n");
+        host_packet_length = -1;
+    } else if (rv == -3) {
+        LOG_PRINTF("Got double null byte from host\n");
+    } else if (rv < 0) {
+        LOG_PRINTF("Host interface COBS framing error\n");
+        host_packet_length = -1;
+    } else if (rv > 0) {
+        host_packet_length = rv;
+    } /* else just return and wait for next byte */
+    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);
+}
+