From 52112f19821f6f667c51f3ac2c68da41365e0b43 Mon Sep 17 00:00:00 2001
From: Sadeep Madurange <sadeep@asciimx.com>
Date: Fri, 11 Apr 2025 13:25:11 +0800
Subject: wip: some packets are being exchanged, after about 3 packets they
 fail (WDT)

---
 ding.c | 43 ++++++++++++++++++++++++++++++++++++++-----
 dong.c | 12 +++++++++---
 nrfm.c | 35 +++++++++++++++++++++++++++--------
 util.c |  8 ++++++++
 util.h |  2 ++
 5 files changed, 84 insertions(+), 16 deletions(-)

diff --git a/ding.c b/ding.c
index 34ff38c..2bf9fe6 100644
--- a/ding.c
+++ b/ding.c
@@ -1,6 +1,7 @@
 #include <stdint.h>
 #include <string.h>
 
+#include <avr/interrupt.h>
 #include <avr/wdt.h>
 #include <util/delay.h>
 
@@ -8,24 +9,56 @@
 #include "uart.h"
 #include "util.h"
 
+#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
+
+static volatile int rxdr = 0;
+
 int main(void)
 {
-	const char *s = "hello world!";
-	uint8_t slen = strlen(s);
+	uint8_t n;
+	char buf[MAXPDLEN + 1];
 
 	uint8_t rxaddr[ADDRLEN] = { 194, 178, 82 };
 	uint8_t txaddr[ADDRLEN] = { 194, 178, 83 };
 
-	wdt_init();
+	//wdt_stop();
 	uart_init();
 	radio_init(rxaddr);
 	radio_print_config();
 
+	sei();
+	radio_listen();
+
+	_delay_ms(2000);
+	radio_sendto(txaddr, "SYN", 3);
+
 	for (;;) {
-		radio_sendto(txaddr, s, slen);
-		wdt_reset();
+		if (rxdr) {
+			n = radio_recv(buf, MAXPDLEN);
+			buf[n] = '\0';
+			rxdr = 0;
+			if (strncmp(buf, "ACK", 3) == 0) {
+				uart_write("INFO: ");
+				uart_write_line(buf);
+			}
+		} else {
+			uart_write_line("No IRQ");
+		}
+
 		_delay_ms(2000);
+		radio_sendto(txaddr, "SYN", 3);
 	}
 
 	return 0;
 }
+
+ISR(RX_PCINTVEC)
+{
+	rxdr = 1;
+}
diff --git a/dong.c b/dong.c
index 1ef872f..fbe4b19 100644
--- a/dong.c
+++ b/dong.c
@@ -1,10 +1,13 @@
 #include <stdint.h>
 #include <string.h>
+
 #include <avr/interrupt.h>
+#include <avr/wdt.h>
 #include <util/delay.h>
 
 #include "nrfm.h"
 #include "uart.h"
+#include "util.h"
 
 #define RX_PIN         PD7
 #define RX_DDR         DDRD
@@ -22,12 +25,14 @@ int main(void)
 	char buf[MAXPDLEN + 1];
 
 	uint8_t rxaddr[] = { 194, 178, 83 };
+	uint8_t txaddr[] = { 194, 178, 82 };
 
 	RX_DDR &= ~(1 << RX_PIN);
 	RX_PORT |= (1 << RX_PIN); 
 	PCICR |= (1 << RX_PCIE);
 	RX_PCMSK |= (1 << RX_PCINT);
 
+	wdt_stop();
 	uart_init();
 	radio_init(rxaddr);
 	radio_print_config();
@@ -37,18 +42,19 @@ int main(void)
 
 	for (;;) {
 		if (rxdr) {
-			uart_write_line("IRQ recv, reading data");
 			n = radio_recv(buf, MAXPDLEN);
 			buf[n] = '\0';
 			rxdr = 0;
-			if (n > 0) {
+			if (strncmp(buf, "SYN", 3) == 0) {
 				uart_write("INFO: ");
 				uart_write_line(buf);
+				radio_sendto(txaddr, "ACK", 3);
 			}
 		} else {
 			uart_write_line("No IRQ");
-			_delay_ms(2000);
 		}
+
+		_delay_ms(1000);
 	}
 
 	return 0;
diff --git a/nrfm.c b/nrfm.c
index 84f790a..de9d132 100644
--- a/nrfm.c
+++ b/nrfm.c
@@ -79,6 +79,22 @@ static inline void read_reg_bulk(uint8_t reg, uint8_t *data, uint8_t n)
 	SPI_PORT |= (1 << SPI_SS);
 }
 
+static inline void write_reg_bulk(uint8_t reg, const uint8_t *data, uint8_t n)
+{
+	int i;
+
+	SPI_PORT &= ~(1 << SPI_SS);
+	SPDR = (reg & 0x1F) | W_REGISTER;
+	while (!(SPSR & (1 << SPIF)))
+		;
+	for (i = 0; i < n; i++) {
+		SPDR = data[i];
+		while (!(SPSR & (1 << SPIF)))
+			;
+	}
+	SPI_PORT |= (1 << SPI_SS);
+}
+
 static inline void setaddr(uint8_t reg, const uint8_t addr[ADDRLEN])
 {
 	int i;
@@ -221,11 +237,18 @@ void radio_init(const uint8_t rxaddr[ADDRLEN])
 	setaddr(0x0A, rxaddr);
 }
 
+void radio_listen(void)
+{
+	disable_chip();
+	rx_mode();
+	enable_chip();
+}
+
 void radio_sendto(const uint8_t addr[ADDRLEN], const char *msg, uint8_t n)
 {
 	char s[4];
 	int i, imax;
-	uint8_t cfg, rv, maxrt, txds;
+	uint8_t cfg, rv, maxrt, txds, rxaddr[ADDRLEN];
 
 	disable_chip();
 
@@ -235,6 +258,7 @@ void radio_sendto(const uint8_t addr[ADDRLEN], const char *msg, uint8_t n)
 	flush_tx();
 	reset_irqs();
 
+	read_reg_bulk(0x0A, rxaddr, ADDRLEN);
 	setaddr(0x10, addr);
 	setaddr(0x0A, addr);
 
@@ -276,14 +300,9 @@ void radio_sendto(const uint8_t addr[ADDRLEN], const char *msg, uint8_t n)
 		uart_write_line("ERROR: sendto() failed: MAX_RT");
 	}
 
+	// restore config, typically rx mode
 	write_reg(0x00, cfg);
-	_delay_ms(MODCHG_DELAY_MS);
-}
-
-void radio_listen(void)
-{
-	disable_chip();
-	rx_mode();
+	write_reg_bulk(0x0A, rxaddr, ADDRLEN);
 	enable_chip();
 }
 
diff --git a/util.c b/util.c
index ddfdf04..fa208a5 100644
--- a/util.c
+++ b/util.c
@@ -8,3 +8,11 @@ void wdt_init(void)
 	WDTCSR |= (1 << WDCE) | (1 << WDE);
 	WDTCSR = (1 << WDE) | (1 << WDP3) | (1 << WDP0);
 }
+
+void wdt_stop(void)
+{
+	wdt_reset();
+	MCUSR &= ~(1<<WDRF);
+	WDTCSR |= (1<<WDCE) | (1<<WDE);
+	WDTCSR = 0x00;
+}
diff --git a/util.h b/util.h
index 75cd9ad..71f3852 100644
--- a/util.h
+++ b/util.h
@@ -3,4 +3,6 @@
 
 void wdt_init(void);
 
+void wdt_stop(void);
+
 #endif
-- 
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