Subject:
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Re: I2C device for the RCX
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Newsgroups:
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lugnet.robotics
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Date:
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Tue, 14 Jan 2003 20:52:59 GMT
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Viewed:
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1156 times
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In lugnet.robotics, Bastiaan van Kesteren writes:
> Now that we are talking about speed, what is the speed of the LepoMux?
> The website seems to be down, so I can't check it out myself. You guys
> made the clock signal at the motor port, and made it better by hacking
> into BrickOS. What speed came out of it? (yust to know what can be done
> whit it, and to see whether its worth all the trouble...)
Lepomux works with a serial protocol (5 bit preamble, 8 bit data, parity) based
on a halfbit-clockspeed of 1 kHz. So compared to your I2C-driver it is dead
slow (about 33ms/byte = 30 bytes/s). This slow speed has two reasons:
- it's possible to do a full-speed write to the motor drivers, but it won't
make sense. As far as I know, there are capacitors connected to the motorports
which completely spoil you signal at high clockrates (schmitt-triggers may
help, a dummy-load didn't).
- brickOS multitasks and does a lot of stuff in its system interrupt. I didn't
want to spend too much time in the motor handler cause that could stop the rest
of the system.
Some days ago we had another idea of how to transfer about 100 bytes/s without
a kernel patch (that should even work with NQC).
Did you calculate the time needed to send/receive one of you I2C-bytes by
looking at the H8 machine-cycles?
Did you run any tests on the multitasking behaviour of the system?
The datarates you got are quite impressing though.
BTW: our server is up again (although the provider was the bad guy - not the
server).
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Message has 1 Reply:
 | | Re: I2C device for the RCX
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| (...) Well, one reason for this is that I2C doesn't need a precise clocksignal (thanks to Dick Swan for telling me, I totally forgot about it). All the timer stuff shouldn't matter for the I2C device, so there should be even higher speeds possible, (...) (22 years ago, 15-Jan-03, to lugnet.robotics)
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Message is in Reply To:
| | Re: I2C device for the RCX
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| Dick Swan wrote: >I don't understand your references to clock pulses. The I2C protocol >is edge triggered with a data bit transferred as the clock signal >transitions from a LOW to HIGH value. Where do clock pulses come into >play? OK, as a (...) (22 years ago, 14-Jan-03, to lugnet.robotics)
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