From 914150f707b48bae0b5950424afdd78faf467b54 Mon Sep 17 00:00:00 2001
From: Olaf Rempel <razzor@kopf-tisch.de>
Date: Fri, 21 Sep 2007 21:39:09 +0200
Subject: [PATCH] initial commit

---
 .gitignore |   6 ++
 Makefile   |  44 ++++++++
 main.c     | 294 +++++++++++++++++++++++++++++++++++++++++++++++++++++
 3 files changed, 344 insertions(+)
 create mode 100644 .gitignore
 create mode 100644 Makefile
 create mode 100644 main.c

diff --git a/.gitignore b/.gitignore
new file mode 100644
index 0000000..6d36148
--- /dev/null
+++ b/.gitignore
@@ -0,0 +1,6 @@
+*.o
+*.elf
+*.bin
+*.hex
+*.lst
+*.map
diff --git a/Makefile b/Makefile
new file mode 100644
index 0000000..cb6161a
--- /dev/null
+++ b/Makefile
@@ -0,0 +1,44 @@
+PRG            = twiboot
+OBJ            = main.o
+MCU_TARGET     = atmega8
+OPTIMIZE       = -Os
+
+DEFS           =
+LIBS           =
+
+# Override is only needed by avr-lib build system.
+override CFLAGS        = -g -Wall $(OPTIMIZE) -mmcu=$(MCU_TARGET) $(DEFS)
+override LDFLAGS       = -Wl,-Map,$(PRG).map,--section-start=.text=0x1C00
+
+CC             = avr-gcc
+OBJCOPY        = avr-objcopy
+OBJDUMP        = avr-objdump
+SIZE           = avr-size
+
+all: $(PRG).elf lst text
+	$(SIZE) -x -A $(PRG).elf
+
+$(PRG).elf: $(OBJ)
+	$(CC) $(CFLAGS) $(LDFLAGS) -o $@ $^ $(LIBS)
+
+clean:
+	rm -rf *.o *.lst *.map $(PRG).elf *.hex *.bin
+
+lst:  $(PRG).lst
+
+%.lst: %.elf
+	$(OBJDUMP) -h -S $< > $@
+
+text: hex bin
+
+hex:  $(PRG).hex
+bin:  $(PRG).bin
+
+%.hex: %.elf
+	$(OBJCOPY) -j .text -j .data -O ihex $< $@
+
+%.bin: %.elf
+	$(OBJCOPY) -j .text -j .data -O binary $< $@
+
+install: text
+	uisp -dprog=avr910 -dserial=/dev/ttyS0 -dspeed=115200 -dpart=M8 --erase --upload if=$(PRG).hex
diff --git a/main.c b/main.c
new file mode 100644
index 0000000..be91d8c
--- /dev/null
+++ b/main.c
@@ -0,0 +1,294 @@
+/***************************************************************************
+ *   Copyright (C) 09/2007 by Olaf Rempel                                  *
+ *   razzor@kopf-tisch.de                                                  *
+ *                                                                         *
+ *   This program is free software; you can redistribute it and/or modify  *
+ *   it under the terms of the GNU General Public License as published by  *
+ *   the Free Software Foundation; version 2 of the License,               *
+ *                                                                         *
+ *   This program is distributed in the hope that it will be useful,       *
+ *   but WITHOUT ANY WARRANTY; without even the implied warranty of        *
+ *   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the         *
+ *   GNU General Public License for more details.                          *
+ *                                                                         *
+ *   You should have received a copy of the GNU General Public License     *
+ *   along with this program; if not, write to the                         *
+ *   Free Software Foundation, Inc.,                                       *
+ *   59 Temple Place - Suite 330, Boston, MA  02111-1307, USA.             *
+ ***************************************************************************/
+#include <avr/io.h>
+#include <avr/interrupt.h>
+#include <avr/boot.h>
+#include <avr/pgmspace.h>
+
+#define F_CPU 8000000
+#include <util/delay.h>
+
+#define LED_RT			(1<<PORTB4)
+#define LED_GN			(1<<PORTB5)
+
+#define TWI_ADDRESS		0x21
+
+#define APP_END			0x1C00
+
+#define CMD_WAIT		0x00
+#define CMD_GET_INFO		0x10
+#define CMD_GET_SIGNATURE	0x11
+#define CMD_WRITE_FLASH		0x12
+#define CMD_READ_FLASH		0x13
+#define CMD_WRITE_EEPROM	0x14
+#define CMD_READ_EEPROM		0x15
+#define CMD_BOOT_APPLICATION	0x1F
+
+/*
+ * LED on PORTB4 blinks with 20Hz (while bootloader is running)
+ * LED on PORTB5 blinks on TWI activity
+ *
+ * bootloader twi-protocol:
+ * - get info about bootloader:
+ *   SLA+W, 0x10, SLA+R, {16 bytes}, STO
+ *
+ * - get signature bytes:
+ *   SLA+W, 0x11, SLA+R, {4 bytes}, STO
+ *
+ * - write one flash page (64bytes on mega8)
+ *   SLA+W, 0x12, addrh, addrl, {64 bytes}, STO
+ *
+ * - read one (or more) flash bytes
+ *   SLA+W, 0x13, addrh, addrl, SLA+R, {* bytes}, STO
+ *
+ * - write one (or more) eeprom bytes
+ *   SLA+W, 0x14, addrh, addrl, {* bytes}, STO
+ *
+ * - read one (or more) eeprom bytes
+ *   SLA+W, 0x15, addrh, addrl, SLA+R, {* bytes}, STO
+ *
+ * - boot application
+ *   SLA+W, 0x1F, STO
+ */
+
+const static uint8_t info[16] = "TWIBOOT m8-v1.0";
+const static uint8_t signature[4] = { 0x1E, 0x93, 0x07, 0x00 };
+
+/* wait 40 * 25ms = 1s */
+volatile static uint8_t boot_timeout = 40;
+volatile static uint8_t cmd = CMD_WAIT;
+
+/* flash buffer */
+static uint8_t buf[SPM_PAGESIZE];
+static uint16_t addr;
+
+void write_flash_page(void)
+{
+	uint16_t pagestart = addr;
+	uint8_t size = SPM_PAGESIZE;
+	uint8_t *p = buf;
+
+	if (pagestart >= APP_END)
+		return;
+
+	boot_page_erase(pagestart);
+	boot_spm_busy_wait();
+
+	do {
+		uint16_t data = *p++;
+		data |= *p++ << 8;
+		boot_page_fill(addr, data);
+
+		addr += 2;
+		size -= 2;
+	} while (size);
+
+	boot_page_write(pagestart);
+	boot_spm_busy_wait();
+	boot_rww_enable();
+}
+
+void write_eeprom_byte(uint8_t val)
+{
+	EEARL = addr;
+	EEARH = (addr >> 8);
+	EEDR = val;
+	addr++;
+
+	EECR |= (1<<EEMWE);
+	EECR |= (1<<EEWE);
+	eeprom_busy_wait();
+}
+
+ISR(TWI_vect)
+{
+	static uint8_t bcnt = 0;
+
+	switch (TWSR & 0xF8) {
+	/* SLA+W received, ACK returned -> receive data and ACK */
+	case 0x60:
+		bcnt = 0;
+ 		PORTB |= LED_RT;
+		TWCR |= (1<<TWINT) | (1<<TWEA);
+		break;
+
+	/* prev. SLA+W, data received, ACK returned -> receive data and ACK */
+	case 0x80:
+		if (bcnt == 0) {
+			cmd = TWDR;
+			switch (cmd) {
+			case CMD_GET_INFO:
+			case CMD_GET_SIGNATURE:
+			case CMD_WRITE_FLASH:
+			case CMD_READ_FLASH:
+				/* abort countdown */
+				boot_timeout = 0;
+
+			case CMD_BOOT_APPLICATION:
+				bcnt++;
+				break;
+
+			default:
+				cmd = CMD_WAIT;
+				bcnt = 0;
+				break;
+			}
+
+		} else if (bcnt == 1) {
+			addr = (TWDR << 8);
+			bcnt++;
+
+		} else if (bcnt == 2) {
+			addr |= TWDR;
+			bcnt++;
+
+		} else if (bcnt >= 3 && cmd == CMD_WRITE_FLASH) {
+			buf[bcnt -3] = TWDR;
+			if (bcnt < sizeof(buf) +2) {
+				bcnt++;
+
+			} else {
+				write_flash_page();
+				bcnt = 0;
+			}
+
+		} else if (bcnt >= 3 && cmd == CMD_WRITE_EEPROM) {
+			write_eeprom_byte(TWDR);
+			bcnt++;
+		}
+
+		TWCR |= (1<<TWINT) | (1<<TWEA);
+		break;
+
+	/* SLA+R received, ACK returned -> send data */
+	case 0xA8:
+		bcnt = 0;
+		PORTB |= LED_RT;
+
+	/* prev. SLA+R, data sent, ACK returned -> send data */
+	case 0xB8:
+		switch (cmd) {
+		case CMD_GET_INFO:
+			TWDR = info[bcnt++];
+			bcnt %= sizeof(info);
+			break;
+
+		case CMD_GET_SIGNATURE:
+			TWDR = signature[bcnt++];
+			bcnt %= sizeof(signature);
+			break;
+
+		case CMD_READ_FLASH:
+			TWDR = pgm_read_byte_near(addr++);
+			break;
+
+		case CMD_READ_EEPROM:
+			EEARL = addr;
+			EEARH = (addr >> 8);
+			EECR |= (1<<EERE);
+			addr++;
+			TWDR = EEDR;
+			break;
+
+		default:
+			TWDR = 0xFF;
+			break;
+		}
+
+		TWCR |= (1<<TWINT) | (1<<TWEA);
+		break;
+
+	/* STOP or repeated START */
+	case 0xA0:
+	/* data sent, NACK returned */
+	case 0xC0:
+		PORTB &= ~LED_RT;
+		TWCR |= (1<<TWINT) | (1<<TWEA);
+		break;
+
+	/* illegal state -> reset hardware */
+	case 0xF8:
+		TWCR |= (1<<TWINT) | (1<<TWSTO) | (1<<TWEA);
+		break;
+	}
+}
+
+ISR(TIMER0_OVF_vect)
+{
+	/* come back in 25ms (@8MHz) */
+	TCNT0 = 0xFF - 195;
+
+	/* blink LED while running */
+	PORTB ^= LED_GN;
+
+	/* count down for app-boot */
+	if (boot_timeout > 1)
+		boot_timeout--;
+
+	/* trigger app-boot */
+	else if (boot_timeout == 1)
+		cmd = CMD_BOOT_APPLICATION;
+}
+
+static void (*jump_to_app)(void) = 0x0000;
+
+int main(void)
+{
+	DDRB = LED_GN | LED_RT;
+	PORTB = LED_GN;
+
+	/* move tnterrupt-vectors to bootloader */
+	GICR = (1<<IVCE);
+	GICR = (1<<IVSEL);
+
+	/* timer0: running with F_CPU/1024 */
+	TCCR0 = (1<<CS02) | (1<<CS00);
+
+	/* enable timer0 OVF interrupt */
+	TIMSK |= (1<<TOIE0);
+
+	/* TWI init: set address, auto ACKs with interrupts */
+	TWAR = (TWI_ADDRESS<<1);
+	TWCR = (1<<TWEA) | (1<<TWEN) | (1<<TWIE);
+
+	sei();
+	while (cmd != CMD_BOOT_APPLICATION);
+	cli();
+
+	/* Disable TWI but keep address! */
+	TWCR = 0x00;
+
+	/* disable timer0 */
+	TIMSK = 0x00;
+	TCCR0 = 0x00;
+
+	/* move interrupt vectors back to application */
+	GICR = (1<<IVCE);
+	GICR = 0x00;
+
+	PORTB = 0x00;
+
+	_delay_ms(25);
+	_delay_ms(25);
+	_delay_ms(25);
+	_delay_ms(25);
+
+	jump_to_app();
+	return 0;
+}