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AP_Var: avoid wearing out EEPROM by re-writing the same value

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when saving a variable, this avoids EEPROM wear by checking if the
existing value is already the same as the value being written, and
avoiding the write.

Thanks to Mike Smith for the implementation

git-svn-id: https://arducopter.googlecode.com/svn/trunk@3233 f9c3cf11-9bcb-44bc-f272-b75c42450872
This commit is contained in:
tridge60@gmail.com 2011-09-04 06:39:49 +00:00
parent e099079cc0
commit 06c4f60490
1 changed files with 17 additions and 1 deletions
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18
libraries/AP_Common/AP_Var.cpp
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@ -207,7 +207,23 @@ bool AP_Var::save(void)
// if it fit in the buffer, save it to EEPROM
if (size <= sizeof(vbuf)) {
debug("saving %u to %u", size, _key);
eeprom_write_block(vbuf, (void *)_key, size);
// XXX this should use eeprom_update_block if/when Arduino moves to
// avr-libc >= 1.7
uint8_t *ep = (uint8_t *)_key;
for (size_t i = 0; i < size; i++, ep++) {
uint8_t newv;
// if value needs to change, change it
if (eeprom_read_byte(ep) != vbuf[i])
eeprom_write_byte(ep, vbuf[i]);
// now read it back
newv = eeprom_read_byte(ep);
if (newv != vbuf[i]) {
debug("readback failed at offset %p: got %u, expected %u",
ep, newv, vbuf[i]);
return false;
}
}
return true;
}
return false;