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OneWire Overdrive?


I suppose that overdrive isn’t included in the OneWire lib? Would it be possible to add? Just duplicates of the WriteBit, WriteByte, ReadBit, ReadByte and Reset but with shorter timing…

We want to move our vending application from the PC to a Cobra. On the PC we currently use standard speed, but it takes around 4 seconds to do transaction due to all the writing required to write the iButton and a secure OneWire device(DS28E01).

The secure device takes the longest because it requires reading one page for calculating the key plus writing a 160bit key back to the DS28E01 to authenticate the write on top of the usual reading and writing commands…

Four seconds doesn’t sound like much, untill there is a que of customers infront of you… :slight_smile:

So? Overdrive? :slight_smile:



You said 4 seconds on pc but how long on fez?

If you need must have on fez then maybe add a one wire controller. Overdrive has more tight requirements and it will nor preform ideal as it is software generated


I still have to port all the drivers to a Fez.

Will come back with hard numbers when I have ported it.



I have ported the secure stuff, but not the whole application. Writing a page of 32 bytes to the secure chip, excluding calculating the key, takes 1.8 seconds. Also calculating the hash for each 8 bytes takes 0.25 seconds for a total writing time of 2.8 seconds per page.

This still excludes writing 16 pages to the iButton…