From c0766d32115ef8b5e92608555fad55a3618b69da Mon Sep 17 00:00:00 2001
From: Sadeep Madurange <sadeep@asciimx.com>
Date: Mon, 7 Apr 2025 14:32:41 +0800
Subject: frnt logic for radio comms.

---
 lock/frnt.c | 59 ++++++++++++++++++++++++++++++++++++++++++++++++++++-------
 lock/util.c |  9 +++++++++
 lock/util.h | 14 ++++++++++++++
 3 files changed, 75 insertions(+), 7 deletions(-)
 create mode 100644 lock/util.c
 create mode 100644 lock/util.h

(limited to 'lock')

diff --git a/lock/frnt.c b/lock/frnt.c
index d0cfe74..18eac98 100644
--- a/lock/frnt.c
+++ b/lock/frnt.c
@@ -1,28 +1,73 @@
+/* Door front, connected to the fingerprint scanner  */
+
 #include <stdint.h>
 #include <string.h>
 #include <util/delay.h>
 
 #include "nrfm.h"
 #include "uart.h"
+#include "util.h"
 
-int main(void)
+#define RX_PIN       PD7
+#define RX_DDR       DDRD
+#define RX_PORT      PORTD
+#define RX_PCIE      PCIE2
+#define RX_PCINT     PCINT23
+#define RX_PCMSK     PCMSK2
+#define RX_PCINTVEC  PCINT2_vect
+
+// todo: atomic var
+static volatile int rxdr = 0;
+
+static inline void await_reply(void)
 {
-	const char *s = "hello world!";
-	//const char *s = "hello how are you doing? This is supposed to be a very long message!";
-	uint8_t slen = strlen(s);
+	radio_listen();
+	for (i = 0; i < 500 && rxdr == 0; i += 100)
+		_delay_ms(100);
+}
 
+int main(void)
+{
+	uint8_t i;
 	uint8_t rxaddr[ADDRLEN] = { 194, 178, 82 };
 	uint8_t txaddr[ADDRLEN] = { 194, 178, 83 };
 
+	char key[WDLEN + 1], msg[WDLEN + 1];
+
 	uart_init();
 	radio_init(rxaddr);
 	radio_print_config();
 
 	for (;;) {
-		radio_sendto(txaddr, s, slen);
-		_delay_ms(2000);
-	}
+		_delay_ms(2000); /* todo: fingerprint check */
 
+		xor(KEY, SYN, msg, WDLEN);
+		radio_sendto(txaddr, msg, WDLEN);
+		await_reply();
+		if (rxdr) {
+			n = radio_recv(msg, WDLEN);
+			msg[n] = '\0';
+			rxdr = 0;
+
+			xor(KEY, msg, key, WDLEN);
+			xor(key, LOCK, msg, WDLEN);
+			radio_sendto(txaddr, msg, WDLEN);
+			await_reply();
+			if (rxdr) {
+				n = radio_recv(msg, WDLEN);
+				msg[n] = '\0';
+				rxdr = 0;
+				uart_write_line(msg);
+			}
+		} else {
+			// power down
+		}
+	}
 
 	return 0;
 }
+
+ISR(RX_PCINTVEC)
+{
+	rxdr = 1;
+}
diff --git a/lock/util.c b/lock/util.c
new file mode 100644
index 0000000..e9a7a5a
--- /dev/null
+++ b/lock/util.c
@@ -0,0 +1,9 @@
+#include "util.h"
+
+void xor(const char *k, const char *s, char *d, int n)
+{
+	int i;
+
+	for (i = 0; i < n; i++)
+		d[i] = s[i] ^ k[i];
+}
diff --git a/lock/util.h b/lock/util.h
new file mode 100644
index 0000000..3f6d7a2
--- /dev/null
+++ b/lock/util.h
@@ -0,0 +1,14 @@
+#ifndef MY_UTIL_H
+#define MY_UTIL_H
+
+#define WDLEN  32
+
+#define KEY       "dM>}jdb,6gsnC$J^K 8(I5vyPemPs%;K"
+#define SYN       "43iqr5$NB8SpN?Z/52{iVl>o|i!.'dsT"
+#define LOCK      "R,I7l^E4j]KyLR9'*Q{Jd'zu.~!84}Ij"
+#define LOCKED    "R,I7l^E4j]KyLR9'*Q{Jd'zu.~!84}Ik"
+#define UNLOCKED  "R,I7l^E4j]KyLR9'*Q{Jd'zu.~!84}Il"
+
+void xor(const char *k, const char *s, char *d, uint8_t n);
+
+#endif /* MY_UTIL_H */
-- 
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