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Implement new, Arduino Leonardo-style reset signal.
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In addition to a negative edge on DTR + "1EAF", we now accept the
Arduino Leonardo style of closing the connection to the board when the
baud rate is set to 1200.

Signed-off-by: Marti Bolivar <mbolivar@leaflabs.com>
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Marti Bolivar committed Aug 4, 2012
1 parent a97e9c1 commit df546c1
Showing 1 changed file with 93 additions and 36 deletions.
129 changes: 93 additions & 36 deletions wirish/usb_serial.cpp
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Expand Up @@ -143,7 +143,81 @@ USBSerial SerialUSB;
#endif

/*
* Bootloader hook implementations
* Bootloader reset hooks
*/

// These hooks are for the reset sequence where you make a negative
// edge on DTR, then send "1EAF" in-band.
static void dtrPlusMagicBytesIfaceHook(unsigned, void*);
static void dtrPlusMagicBytesRXHook(unsigned, void*);

// These hooks are for the reset sequence where the host PC closes its
// connection after setting the baud rate to 1200.
static void magicBaudIfaceHook(unsigned, void*);
#define magicBaudRXHook(request, data) ((void)0) // nop

// FIXME remove the LED toggle; it's for debugging
#include <wirish/wirish.h>
static void ifaceSetupHook(unsigned hook, void *requestvp) {
digitalWrite(BOARD_LED_PIN, HIGH);
// TODO remove old reset scheme?
dtrPlusMagicBytesIfaceHook(hook, requestvp);
magicBaudIfaceHook(hook, requestvp);
}

static void rxHook(unsigned hook, void *requestvp) {
// TODO remove old reset scheme?
dtrPlusMagicBytesRXHook(hook, requestvp);
magicBaudRXHook(hook, requestvp);
}

/*
* Reset hook helpers
*/

#define RESET_DELAY 100000
static void wait_reset(void) {
delay_us(RESET_DELAY);
nvic_sys_reset();
}

#define STACK_TOP 0x20000800
#define EXC_RETURN 0xFFFFFFF9
#define DEFAULT_CPSR 0x61000000

// This macro resets the board when in interrupt context.
#define RESET_INTO_BOOTLOADER() \
do { \
/* Target address is wait_reset's, but set the thumb bit. */ \
unsigned int target = (unsigned int)wait_reset | 0x1; \
delay_us(RESET_DELAY); \
asm volatile("mov r0, %[stack_top] \n\t" /* Reset stack */ \
"mov sp, r0 \n\t" \
"mov r0, #1 \n\t" \
"mov r1, %[target_addr] \n\t" \
"mov r2, %[cpsr] \n\t" \
"push {r2} \n\t" /* Fake xPSR */ \
"push {r1} \n\t" /* PC target addr */ \
"push {r0} \n\t" /* Fake LR */ \
"push {r0} \n\t" /* Fake R12 */ \
"push {r0} \n\t" /* Fake R3 */ \
"push {r0} \n\t" /* Fake R2 */ \
"push {r0} \n\t" /* Fake R1 */ \
"push {r0} \n\t" /* Fake R0 */ \
"mov lr, %[exc_return] \n\t" \
"bx lr" \
: \
: [stack_top] "r" (STACK_TOP), \
[target_addr] "r" (target), \
[exc_return] "r" (EXC_RETURN), \
[cpsr] "r" (DEFAULT_CPSR) \
: "r0", "r1", "r2"); \
/* We never get here */ \
ASSERT_FAULT(0); \
} while (0)

/*
* DTR + "1EAF" hooks
*/

enum reset_state_t {
Expand All @@ -155,7 +229,7 @@ enum reset_state_t {

static reset_state_t reset_state = DTR_UNSET;

static void ifaceSetupHook(unsigned hook, void *requestvp) {
static void dtrPlusMagicBytesIfaceHook(unsigned hook, void *requestvp) {
uint8 request = *(uint8*)requestvp;

// Ignore requests we're not interested in.
Expand All @@ -182,16 +256,7 @@ static void ifaceSetupHook(unsigned hook, void *requestvp) {
}
}

#define RESET_DELAY 100000
static void wait_reset(void) {
delay_us(RESET_DELAY);
nvic_sys_reset();
}

#define STACK_TOP 0x20000800
#define EXC_RETURN 0xFFFFFFF9
#define DEFAULT_CPSR 0x61000000
static void rxHook(unsigned hook, void *ignored) {
static void dtrPlusMagicBytesRXHook(unsigned hook, void *ignored) {
/* FIXME this is mad buggy; we need a new reset sequence. E.g. NAK
* after each RX means you can't reset if any bytes are waiting. */
if (reset_state == DTR_NEGEDGE) {
Expand All @@ -214,31 +279,23 @@ static void rxHook(unsigned hook, void *ignored) {

// Got the magic sequence? Reset, presumably into the bootloader.
if (cmpMatch) {
// Return address is wait_reset, but we must set the thumb bit.
unsigned int target = (unsigned int)wait_reset | 0x1;
asm volatile("mov r0, %[stack_top] \n\t" // Reset stack
"mov sp, r0 \n\t"
"mov r0, #1 \n\t"
"mov r1, %[target_addr] \n\t"
"mov r2, %[cpsr] \n\t"
"push {r2} \n\t" // Fake xPSR
"push {r1} \n\t" // PC target addr
"push {r0} \n\t" // Fake LR
"push {r0} \n\t" // Fake R12
"push {r0} \n\t" // Fake R3
"push {r0} \n\t" // Fake R2
"push {r0} \n\t" // Fake R1
"push {r0} \n\t" // Fake R0
"mov lr, %[exc_return] \n\t"
"bx lr"
:
: [stack_top] "r" (STACK_TOP),
[target_addr] "r" (target),
[exc_return] "r" (EXC_RETURN),
[cpsr] "r" (DEFAULT_CPSR)
: "r0", "r1", "r2");
/* should never get here */
RESET_INTO_BOOTLOADER();
}
}
}
}

/*
* 1200 baud + close hooks
*/


#define MAGIC_RESET_BAUD 1200
static void magicBaudIfaceHook(unsigned hook, void *requestvp) {
// Reset sequence is to set the baud rate to 1200 and then close
// the port.
if ((usb_cdcacm_get_baud() == MAGIC_RESET_BAUD) &&
usb_cdcacm_get_dtr() == 0) {
RESET_INTO_BOOTLOADER();
}
}

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