RESET protocol to jump from application to boot loader without power cycling

PROTOCOL

@@ -7,6 +7,8 @@ Protocol
 
    1	0	0	Pong (maybe return version string in the future)
 
+   2	0	0	Reset (64 bytes reset secret)
+
    4	0	N	Unlock secret (64 bytes payload)
    4	1..N-1	N	Firmware binary (64 bytes payload)
    4	N	N	First half of hash

fw/Makefile

@@ -30,7 +30,7 @@ OBJCOPY = $(AVR_PREFIX)objcopy
 #OBJDUMP = $(AVR_PREFIX)objdump
 SIZE = $(AVR_PREFIX)size
 
-OBJS = $(NAME).o dispatch.o hash.o $(COMMON_OBJS)
+OBJS = $(NAME).o dispatch.o hash.o reset.o $(COMMON_OBJS)
 BOOT_OBJS = boot.o flash.o fw.o $(COMMON_OBJS)
 COMMON_OBJS = rf.o spi.o
 
@@ -87,7 +87,7 @@ clean:
 		rm -f version.c version.d version.o
 
 nosecrets:
-		rm -f unlock-secret.inc image-secret.inc
+		rm -f unlock-secret.inc reset-secret.inc image-secret.inc
 
 # ----- Build version ---------------------------------------------------------
 
@@ -129,10 +129,14 @@ SECRET = { dd if=$(RANDOM) iflag=fullblock bs=$(1) count=1 status=noxfer | \
 unlock-secret.inc:
 		$(BUILD) $(call SECRET,64) >$@ || { rm -f $@; exit 1; }
 
+reset-secret.inc:
+		$(BUILD) $(call SECRET,64) >$@ || { rm -f $@; exit 1; }
+
 image-secret.inc:
 		$(BUILD) $(call SECRET,128) >$@ || { rm -f $@; exit 1; }
 
 fw.o:		unlock-secret.inc
+reset.o:	unlock-secret.inc
 
 # ----- Dependencies ----------------------------------------------------------
 

fw/antorcha.c

@@ -23,8 +23,8 @@
 #include "dispatch.h"
 
 
-
 static const struct handler *protos[] = {
+	&reset_handler,
 	NULL
 };
 
@@ -39,12 +39,6 @@ int main(void)
 	 * It has also brought up RF and the underlying SPI.
 	 */
 
-while (1) {
-	SET(LED_B8);
-	_delay_ms(100);
-	CLR(LED_B8);
-	_delay_ms(100);
-}
 	while (1) {
 		got = rf_recv(buf, sizeof(buf));
 		if (got > 2)

fw/boot.c

@@ -57,9 +57,19 @@ int main(void)
 	PORTD = 0;
 	DDRD = 0xff;
 
-	/* disable pull-ups */
+	/* Disable pull-ups */
 	MCUCR |= 1 << PUD;
 
+	/*
+	 * Disable the watchdog timer, in case the boot loader has been
+	 * entered by a watchdog reset commanded by the application.
+	 */
+
+	MCUSR = 0;		/* Remove override */
+	WDTCSR |= 1 << WDCE;	/* Enable change */
+	WDTCSR = 1 << WDCE;	/* Disable watchdog while still enabling
+				   change */
+
 	rf_init();
 
 	/*

fw/dispatch.h

@@ -26,6 +26,8 @@ struct handler {
 };
 
 
+extern struct handler reset_handler;
+
 bool dispatch(const uint8_t *buf, uint8_t len, const struct handler **protos);
 
 #endif /* !PROTO_H */

fw/fw.c

@@ -15,6 +15,9 @@
 #include <stdint.h>
 #include <string.h>
 
+#define F_CPU   8000000UL
+#include <util/delay.h>
+
 #include "io.h"
 #include "flash.h"
 #include "proto.h"
@@ -54,8 +57,9 @@ bool fw_packet(const uint8_t *buf, uint8_t len)
 	static uint8_t limit;
 	uint8_t ack[] = { FIRMWARE+1, buf[1], buf[2] };
 
-	/* short (barely visible) flash to indicate reception */
+	/* short flash to indicate reception */
 	SET(LED_B7);
+	_delay_ms(1);
 	CLR(LED_B7);
 
 	/* Check packet for formal validity */

fw/proto.h

@@ -18,6 +18,7 @@
 enum pck_type {
 	PING		= 0,	/* version query */
 	PONG		= 1,	/* version response */
+	RESET		= 2,	/* reset to boot loader */
 	FIRMWARE	= 4,	/* firmware upload */
 	FIRMWARE_ACK	= 5,	/* firmware upload acknowledgement */
 	IMAGE		= 6,	/* image upload */

tools/antorcha.c

@@ -49,6 +49,7 @@ static void rf_send(struct atrf_dsc *dsc, void *buf, int len)
 	/* Copy the message to append the CRC placeholders */
 	memcpy(tmp, buf, len);
 	atrf_reg_write(dsc, REG_TRX_STATE, TRX_CMD_PLL_ON);
+	flush_interrupts(dsc);
 	atrf_buf_write(dsc, tmp, len+2);
 	atrf_reg_write(dsc, REG_TRX_STATE, TRX_CMD_TX_START);
 	wait_for_interrupt(dsc, IRQ_TRX_END,
@@ -98,17 +99,25 @@ static void ping(struct atrf_dsc *dsc)
 }
 
 
-static void packet(struct atrf_dsc *dsc,
+static void packet_noack(struct atrf_dsc *dsc,
     uint8_t type, uint8_t seq, uint8_t last, const void *payload, int len)
 {
 	uint8_t tx_buf[PAYLOAD+3] = { type, seq, last };
-	uint8_t rx_buf[10];
-	int got;
 
 	assert(len == PAYLOAD);
 	memcpy(tx_buf+3, payload, len);
+	rf_send(dsc, tx_buf, sizeof(tx_buf));
+}
+
+
+static void packet(struct atrf_dsc *dsc,
+    uint8_t type, uint8_t seq, uint8_t last, const void *payload, int len)
+{
+	uint8_t rx_buf[10];
+	int got;
+
 	while (1) {
-		rf_send(dsc, tx_buf, sizeof(tx_buf));
+		packet_noack(dsc, type, seq, last, payload, len);
 		if (verbose)
 			write(2, ">", 1);
 		got = rf_recv(dsc, rx_buf, sizeof(rx_buf));
@@ -146,6 +155,7 @@ static void send_firmware(struct atrf_dsc *dsc, void *buf, int len)
 		write(2, "firmware ", 9);
 	last = (len+63)/64;
 	seq = 0;
+	packet_noack(dsc, RESET, 0, 0, unlock_secret, PAYLOAD);
 	packet(dsc, FIRMWARE, seq++, last, unlock_secret, PAYLOAD);
 	while (len >= PAYLOAD) {
 		packet(dsc, FIRMWARE, seq++, last, buf, PAYLOAD);