Asyncronous 1-wire interface?
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From: Leo Havmøller on 29 Apr 2010 00:48 Hi, Im looking for a short-range (20 cm) 1-wire I/O interface that is fully asyncronous. Does such a thing exist? Leo Havm�ller.
From: DJ Delorie on 29 Apr 2010 01:09 How fast does it need to be? Does it need to be bidirectional? Have you looked at 1-wire? Even standard serial can be used if the two ends coordinate who's transmitting and who's receiving. A small resistor between them protects against both sides transmitting at the same time.
From: Leo Havmøller on 29 Apr 2010 03:03 "DJ Delorie" <dj(a)delorie.com> wrote in message news:1KmdnZvCP-HziUTWnZ2dnUVZ_uWdnZ2d(a)giganews.com... > How fast does it need to be? The master will probably clock it between 1-10MHz. > Does it need to be bidirectional? Yes. > Have you looked at 1-wire? Yes, its syncronous => no good. > Even standard serial can be used if the two ends coordinate who's > transmitting and who's receiving. Also syncronous. > A small resistor between them protects against both sides transmitting at > the same time. Yes. Some further information: - The master always controls what happens on the "bus". - The slave has no clock with a fixed frequency that can be used => the interface must be asyncronous. - An equivalent interface with 2 wires would be e.g. I2C i.e. 1 wire for clock, 1 wire for I/O. Leo Havm�ller.
From: Meindert Sprang on 29 Apr 2010 04:01 "Leo Havm�ller" <rtxleh(a)nospam.nospam> wrote in message news:hrbb0e$7tn$1(a)speranza.aioe.org... > "DJ Delorie" <dj(a)delorie.com> wrote in message > news:1KmdnZvCP-HziUTWnZ2dnUVZ_uWdnZ2d(a)giganews.com... > > How fast does it need to be? > The master will probably clock it between 1-10MHz. > > > Does it need to be bidirectional? > Yes. Two standard async UARTS, all TX and RX signals harwire-orred together with a pull-up. > > Have you looked at 1-wire? > Yes, its syncronous => no good. > > > Even standard serial can be used if the two ends coordinate who's > > transmitting and who's receiving. > Also syncronous. Errmm... in my opinion, "standard serial" is mostly asynchronous. > - The slave has no clock with a fixed frequency that can be used => the > interface must be asyncronous. Does the slave have a clock at all? Meindert
From: Leo Havmøller on 29 Apr 2010 04:39
> Errmm... in my opinion, "standard serial" is mostly asynchronous. Then im probably using the wrong term. A serial port is locked to a baudrate => a fixed clock is needed to derive the baudrate. E.g. for a 2-wire I2C interface the clock is provided by the master i.e. the slave does not need a fixed clock to drive or sample the I/O pin. >> - The slave has no clock with a fixed frequency that can be used => the >> interface must be asyncronous. > > Does the slave have a clock at all? Yes, it even has a crystal ;-) Due to power saving the clocks are changed up and down all the time => no fixed clock is available. Leo Havm�ller. |