From d0113cf3d4ac0dbf47bdba27babf1e4c3f918a26 Mon Sep 17 00:00:00 2001
From: Sadeep Madurange <sadeep@asciimx.com>
Date: Sun, 30 Mar 2025 19:39:53 +0800
Subject: sendto()

---
 main.c |  7 ++++++-
 nrfm.c | 48 ++++++++++++++++++++++++++++++++++++------------
 nrfm.h |  6 ++++--
 3 files changed, 46 insertions(+), 15 deletions(-)

diff --git a/main.c b/main.c
index e1046dd..8c108a7 100644
--- a/main.c
+++ b/main.c
@@ -1,15 +1,20 @@
 #include <stdint.h>
+#include <string.h>
 
 #include "nrfm.h"
 #include "uart.h"
 
 int main(void)
 {
-	uint8_t rxaddr[] = { 82, 178, 194 };  /* 194.178.82 */
+	const char *s = "hello world!";
+
+	uint8_t rxaddr[] = { 194, 178, 82 };
+	uint8_t txaddr[] = { 194, 178, 83 };
 
 	uart_init();
 	radio_init(rxaddr);
 	radio_print_config();
+	radio_sendto(txaddr, s, strlen(s));
 
 	return 0;
 }
diff --git a/nrfm.c b/nrfm.c
index cc81dbe..e05c858 100644
--- a/nrfm.c
+++ b/nrfm.c
@@ -31,8 +31,7 @@
 #define NRF_R_REGISTER   0x1F
 #define NRF_W_REGISTER   0x20
 
-#define PDLEN    33
-#define ADDRLEN   3
+#define MAXPDLEN   32
 
 #define LEN(a)  (sizeof(a) / sizeof(a[0]))
 
@@ -85,7 +84,7 @@ static inline void read_reg_bulk(uint8_t reg, uint8_t *data, uint8_t n)
 	SPI_PORT |= (1 << SPI_SS);
 }
 
-static inline void set_addr(uint8_t reg, uint8_t addr[ADDRLEN])
+static inline void setaddr(uint8_t reg, const uint8_t addr[ADDRLEN])
 {
 	uint8_t i;
 
@@ -94,13 +93,36 @@ static inline void set_addr(uint8_t reg, uint8_t addr[ADDRLEN])
 	while (!(SPSR & (1 << SPIF)))
 		;
 	for (i = ADDRLEN - 1; i >= 0; i--) {
-		SPDR = data[i];
+		SPDR = addr[i];
 		while (!(SPSR & (1 << SPIF)))
 			;
 	}
 	SPI_PORT |= (1 << SPI_SS);
 }
 
+static inline void send(const void *msg, uint8_t n)
+{
+	uint8_t i;
+
+	if (n > MAXPDLEN)
+		n = MAXPDLEN;
+
+	SPI_PORT &= ~(1 << SPI_SS);
+	SPDR = 0xA0;
+	while (!(SPSR & (1 << SPIF)))
+		;
+	for (i = n - 1; i >= 0; i--) {
+		SPDR = ((uint8_t *)msg)[i];
+		while (!(SPSR & (1 << SPIF)))
+			;
+	}
+	SPI_PORT |= (1 << SPI_SS);
+
+	NRF_CE_PORT |= (1 << NRF_CE);
+	_delay_us(10);
+	NRF_CE_PORT &= ~(1 << NRF_CE);
+}
+
 void radio_print_config(void)
 {
 	char s[22];
@@ -125,7 +147,7 @@ void radio_print_config(void)
 	uart_write_line(s);
 }
 
-void radio_init(uint8_t rxaddr[ADDRLEN])
+void radio_init(const uint8_t rxaddr[ADDRLEN])
 {
 	SPI_DDR |= (1 << SPI_SS) | (1 << SPI_SCK) | (1 << SPI_MOSI);
 	SPI_PORT |= (1 << SPI_SS);
@@ -152,21 +174,23 @@ void radio_init(uint8_t rxaddr[ADDRLEN])
 	write_reg(0x1D, 0b00000100);  /* enable dynamic payload length */
 	write_reg(0x1C, 0b00000001);  /* enable dynamic payload length for pipe 0 */
 
-	set_addr(0x0A, rxaddr);
+	setaddr(0x0A, rxaddr);
 }
 
-void radio_send(uint8_t txaddr[ADDRLEN], void *msg, uint8_t n)
+void radio_sendto(const uint8_t addr[ADDRLEN], const void *msg, uint8_t n)
 {
 	uint8_t rv;
 
 	rv = read_reg(0x00);
 	rv &= ~1;
-	write_reg(0x00, rv); /* enable PTX by setting PRIM_RX low */
-	
-	// todo: check if we need to write the tx address every time
-	set_addr(0x10, txaddr);
-	set_addr(0x0A, txaddr); /* auto-ACK on pipe 0 */
+	write_reg(0x00, rv);
 
+	rv = read_reg(0x07);
+	if (rv & 0x10)
+		write_reg(0x07, rv);
 	
+	setaddr(0x10, addr);
+	setaddr(0x0A, addr);
+	send(msg, n);
 }
 
diff --git a/nrfm.h b/nrfm.h
index 7f5fdb1..ade5205 100644
--- a/nrfm.h
+++ b/nrfm.h
@@ -3,8 +3,10 @@
 
 #include <stdint.h>
 
-void radio_init(uint8_t rxaddr[3]);
+#define ADDRLEN     5
+
+void radio_init(const uint8_t rxaddr[ADDRLEN]);
 void radio_print_config(void);
-void radio_send(uint8_t rxaddr[ADDRLEN], uint8_t *data, uint8_t n);
+void radio_sendto(const uint8_t addr[ADDRLEN], const void *msg, uint8_t n);
 
 #endif /* NRFM_H */
-- 
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