firmware: Minimal frame encodingHEADmain

This only covers the correct frame size, setting the buffer to 0 and
copy the payload over.

Missing is:

- copy destination address
- copy source address
- set frame type
- calculate and add CRC32 checksum

1 files changed, 12 insertions, 0 deletions

diff --git a/firmware/src/data_link.c b/firmware/src/data_link.c
index a6d091a..330e973 100644
--- a/firmware/src/data_link.c
+++ b/firmware/src/data_link.c
@@ -1,7 +1,19 @@
+#include <string.h>
 #include <zephyr/drivers/uart.h>
 
 #include "data_link.h"
 
+ssize_t dl_encode_frame(uint8_t *payload, size_t len, uint8_t *dst) {
+	// FIXME check for maximum size
+
+	size_t flen = 8 + 8 + 2 + len + 4;
+
+	memset(dst, 0, flen);
+	memcpy((void *)(dst + 18), payload, len);
+
+	return flen;
+}
+
 void dl_send_frame(const struct device *const uart_dev, uint8_t *buffer,
                    size_t len) {
 	for (size_t i = 0; i < len; i++) {