Fix SLIP header parsing logic

Author: Kaweees

docs/arduino-uart.png

@@ -44,22 +44,22 @@ typedef enum slip_cmd_t {
 
 /* Represents a SLIP packet header (stored in big-endian/network-order) */
 typedef struct __attribute__((packed)) slip_header_t {
-    /* The length of the payload in bytes */
-    uint16_t length;
-    /* The CRC-CCITT-FALSE of the payload */
-    uint16_t crc;
-    /* The command code */
-    uint8_t cmd;
-    /* The packet ID */
-    uint16_t id;
+  /* The length of the payload in bytes */
+  uint16_t length;
+  /* The CRC-CCITT-FALSE of the payload */
+  uint16_t crc;
+  /* The command code */
+  uint8_t cmd;
+  /* The packet ID */
+  uint16_t id;
 } slip_header_t;
 
 /* Represents a SLIP packet */
 typedef struct slip_packet_t {
-    /* The header of the packet */
-    slip_header_t header;
-    /* The data payload of the packet (static buffer) */
-    uint8_t payload[SLIP_MAX_PAYLOAD_LEN];
+  /* The header of the packet */
+  slip_header_t header;
+  /* The data payload of the packet (static buffer) */
+  uint8_t payload[SLIP_MAX_PAYLOAD_LEN];
 } slip_packet_t;
 
 /* Begin function prototype declarations */

firmware/chipignite/polysat/README.md

@@ -151,14 +151,6 @@ void main() {
 
   // Main loop - echo received characters and blink LED and
   while (1) {
-    // // Check if data is available to read
-    // if (uart_read_available()) {
-    //   // Read and echo back the character
-    //   uint8_t ch = uart_read();
-    //   uart_write(ch);
-    //   slip_send_packet(c, 1, SLIP_CMD_DATA, uart_write);
-    // }
-
     if (!pulse) {
       led_off();
       // Set GPIO 33 low (bit 1)

firmware/chipignite/polysat/include/slip.h

@@ -31,11 +31,16 @@ void slip_send_packet(const uint8_t* data, uint16_t data_len, uint8_t cmd, void
   hdr.length = (uint16_t)data_len;
   hdr.crc = crc16_ccitt_false(data, data_len);
   hdr.cmd = (slip_cmd_t)cmd;
-  hdr.id = packet_count++;
+
+  /* Check if payload length exceeds buffer size */
+  if (data_len > SLIP_MAX_PAYLOAD_LEN) { return; }
 
   /* Write header to buffer */
   uint8_t* buffer = (uint8_t*)&hdr;
-  for (uint16_t i = 0; i < sizeof(hdr); i++) { send_byte(buffer[i]); }
+  for (uint16_t byte = 0; byte < sizeof(hdr); byte++) { send_byte(buffer[byte]); }
+
+  /* Update packet count */
+  packet_count++;
 
   /* SLIP-encode the payload */
   for (uint16_t i = 0; i < data_len; i++) {
@@ -84,12 +89,12 @@ uint16_t crc16_ccitt_false(const uint8_t* data, uint16_t len) {
 void slip_receive_packet(uint8_t input_byte, slip_packet_t* decoded_packet, uint8_t (*read_byte)(void)) {
   if (!decoded_packet || !read_byte) { return; }
 
-  /* Read header fields */
-  decoded_packet->header.length = read_byte() | (read_byte() << 8);
-  decoded_packet->header.crc = read_byte() | (read_byte() << 8);
-  decoded_packet->header.cmd = (slip_cmd_t)read_byte();
-  packet_count = decoded_packet->header.id = read_byte() | (read_byte() << 8);
-  packet_count++;
+  /* Read header from buffer */
+  uint8_t* buffer = (uint8_t*)decoded_packet;
+  for (uint16_t byte = 0; byte < sizeof(*decoded_packet); byte++) { buffer[byte] = read_byte(); }
+
+  /* Update packet count */
+  packet_count = decoded_packet->header.id + 1;
 
   /* Check if payload length exceeds buffer size */
   if (decoded_packet->header.length > SLIP_MAX_PAYLOAD_LEN) {