From 06d40aaae09933a76410f6dd7e7bbc5cba3b599a Mon Sep 17 00:00:00 2001
From: Diogo Diniz <diogocruzdiniz@gmail.com>
Date: Wed, 8 Apr 2026 15:38:19 +0100
Subject: [PATCH] fix: Corrected I3C checksum

---
 app/src/i3c/i3c.c      | 3 +++
 app/src/incp_handler.c | 3 ++-
 2 files changed, 5 insertions(+), 1 deletion(-)

diff --git a/app/src/i3c/i3c.c b/app/src/i3c/i3c.c
index dc58d25..ddcf683 100644
--- a/app/src/i3c/i3c.c
+++ b/app/src/i3c/i3c.c
@@ -6,6 +6,8 @@
 
 #include "checksum.h"
 
+#define OWN_ADDRESS (0x01)
+
 uint8_t i3c_crc(uint8_t dst, uint8_t *msg, size_t len) {
     uint8_t crc;
     crc8_init(&crc);
@@ -25,6 +27,7 @@ bool i3c_validate(uint8_t *msg, size_t len)
     uint8_t rcvd_crc8 = msg[2];
     msg[2] = 0;
     crc8_init(&computed_crc8);
+    crc8_add(&computed_crc8, OWN_ADDRESS);
     crc8_addSlice(&computed_crc8, msg, len);
     crc8_finish(&computed_crc8);
     msg[2] = rcvd_crc8;
diff --git a/app/src/incp_handler.c b/app/src/incp_handler.c
index 7ed4ca1..086c0e2 100644
--- a/app/src/incp_handler.c
+++ b/app/src/incp_handler.c
@@ -28,6 +28,7 @@ void handle_incp(msg_buf_t *msgs)
 	// Check I3C
 	if (!i3c_validate(msg, len))
 	{
+		HAL_GPIO_WritePin(LD2_GPIO_Port, LD2_Pin, GPIO_PIN_SET);
 		//return; // Ignore failed messages
 	}
 
@@ -56,7 +57,7 @@ static void handle_msg(uint8_t sender, uint8_t *bytes, uint32_t len)
 
 		bytes[-3] = I2C_OWN_ADDR;
 		bytes[-2] = len;
-		bytes[-1] = i3c_crc(I2C_OWN_ADDR, bytes, len);
+		bytes[-1] = i3c_crc(sender, bytes-I3C_HEADER_SIZE, len+I3C_HEADER_SIZE);
 		I2C1_transmit_master(sender, bytes-I3C_HEADER_SIZE, len+I3C_HEADER_SIZE);
 		break;