Asyncronous 1-wire interface?
in [Embedded]
|
Prev: Request for help in neew development with AO, DIO, counters and real time
Next: (AT91SAM9260) Where to buy Schukat parts in Italy?
From: Stef on 29 Apr 2010 05:07 In comp.arch.embedded, Leo Havm�ller <rtxleh(a)nospam.nospam> wrote: >> 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. A better term would be variable frequency/baudrate I guess. But that is easiest to achieve with synchronous communication. The clock provides a reference of when to sample the data. But that requires at least 2 wires, like I2C. ;-) >>> - 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. So the clock can change even in the middle of a transmission? I'm not sure there is a way to make asynchronous communication work reliably under those conditions. Maybe you can make it work with things like manchester encoding, but certainly not with standard peripherals. If there is a way to guarantee a fixed frequency during a complete transmission, it might be easier to get it working. But that also requires the receiving side to fix frequency as soon as the first edge of a start bit is detected. -- Stef (remove caps, dashes and .invalid from e-mail address to reply by mail) Given its constituency, the only thing I expect to be "open" about [the Open Software Foundation] is its mouth. -- John Gilmore
From: larwe on 29 Apr 2010 05:09 On Apr 29, 4:39 am, Leo Havmøller <rtx...(a)nospam.nospam> wrote: > Due to power saving the clocks are changed up and down all the time => no > fixed clock is available. Can you assume that the clock will not change during a message? Because if so, the problem is quite easy - it's exactly the same problem as transmitting simple AM radio messages.
From: Nial Stewart on 29 Apr 2010 07:44 "Leo Havm�ller" <rtxleh(a)nospam.nospam> wrote in message news:hrb32b$tm1$1(a)speranza.aioe.org... > Hi, > Im looking for a short-range (20 cm) 1-wire I/O interface that is fully asyncronous. > Does such a thing exist? http://www.1pin-interface.com This transfers data from the module to the PC at 1Mbps and is pretty robust. Nial.
From: Leo Havmøller on 29 Apr 2010 07:59 "Nial Stewart" <nial*REMOVE_THIS*@nialstewartdevelopments.co.uk> wrote in message news:83t9o5F686U1(a)mid.individual.net... > "Leo Havm�ller" <rtxleh(a)nospam.nospam> wrote in message > news:hrb32b$tm1$1(a)speranza.aioe.org... >> Hi, >> Im looking for a short-range (20 cm) 1-wire I/O interface that is fully >> asyncronous. >> Does such a thing exist? > > http://www.1pin-interface.com > > This transfers data from the module to the PC at 1Mbps and is pretty > robust. Also locked to a specific baudrate, so does not fit the requirements. Leo Havm�ller.
From: Grant Edwards on 29 Apr 2010 08:56
On 2010-04-29, Leo Havm?ller <rtxleh(a)nospam.nospam> wrote: > "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. Huh? "Standard serial" (e.g. UART w/ RS-232 driver) is asynchronous, *not* synchronous. -- Grant Edwards grant.b.edwards Yow! I am having FUN... at I wonder if it's NET FUN or gmail.com GROSS FUN? |