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Fix save/restore of magic key location during reset 

In the USB CDC code to invoke an auto-reset, the magic key location could be
restored before it had actually been saved. The sketch would then have a
corrupted value at this location. This fix prevents the value from being
restored if it hasn't previously been saved.
This commit is contained in:
Scott Allen 2017-03-10 14:47:18 -05:00 committed by Martino Facchin
parent b084848f2e
commit 289faaa759
1 changed files with 6 additions and 4 deletions
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10
cores/arduino/CDC.cpp
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@ -119,9 +119,9 @@ bool CDC_Setup(USBSetup& setup)
if (1200 == _usbLineInfo.dwDTERate && (_usbLineInfo.lineState & 0x01) == 0)
{
#if MAGIC_KEY_POS != (RAMEND-1)
// Backup ram value if its not a newer bootloader.
// Backup ram value if its not a newer bootloader and it hasn't already been saved.
// This should avoid memory corruption at least a bit, not fully
if (magic_key_pos != (RAMEND-1)) {
if (magic_key_pos != (RAMEND-1) && *(uint16_t *)magic_key_pos != MAGIC_KEY) {
*(uint16_t *)(RAMEND-1) = *(uint16_t *)magic_key_pos;
}
#endif
@ -129,12 +129,14 @@ bool CDC_Setup(USBSetup& setup)
*(uint16_t *)magic_key_pos = MAGIC_KEY;
wdt_enable(WDTO_120MS);
}
else
else if (*(uint16_t *)magic_key_pos == MAGIC_KEY)
{
// Most OSs do some intermediate steps when configuring ports and DTR can
// twiggle more than once before stabilizing.
// To avoid spurious resets we set the watchdog to 250ms and eventually
// To avoid spurious resets we set the watchdog to 120ms and eventually
// cancel if DTR goes back high.
// Cancellation is only done if an auto-reset was started, which is
// indicated by the magic key having been set.
wdt_disable();
wdt_reset();