 | | Custom Firmware, IR Problems, and Dead RCXs (long)
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The following information is my own opinion and not endorsed or verified in any way by LEGO. That being said, I think that now is the time to relate some experiences I've had over the past couple of months with my RCX and IR tower - and it boils (...) (23 years ago, 27-May-01, to lugnet.robotics)
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| | Re: Custom Firmware, IR Problems, and Dead RCXs (long)
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Oh, geez, this could be bad. Could changing the firmware to reduce comm activity fix this? It seems to be a problem of usage, not specific firmware properties (i.e. constant data uplaoding.) Andy (...) -- See my Visual Interface for leJOS at (URL) (23 years ago, 27-May-01, to lugnet.robotics)
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| | RE: Custom Firmware, IR Problems, and Dead RCXs (long)
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(...) Well, yes and no. The biggest risk is when you use the tower or the RCX in high-power (far) mode for extended transmissions. I was thinking about why we have not received more posts about dead RCXs. My old pbForths (and I think legOS too) set (...) (23 years ago, 27-May-01, to lugnet.robotics)
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| | RE: Custom Firmware, IR Problems, and Dead RCXs (long)
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Hi all, Just a couple a quick comments on this thread - I'm a firmware design engineer who's done lots of work with IrDA. I don't, however, have any experience with the internals of the RCX or the IR Tower, other than owning them and reading this (...) (23 years ago, 27-May-01, to lugnet.robotics)
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| | RE: Custom Firmware, IR Problems, and Dead RCXs (long)
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(...) You are right, but the RCX and the tower are right at the hairy edge. The additional 50R impedance will leave the near mode essentially unchanged and I'll sacrifice on the high range. Start with the tower. If you use a 9V battery, the IR (...) (23 years ago, 28-May-01, to lugnet.robotics)
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| | RE: Custom Firmware, IR Problems, and Dead RCXs
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Ralph, Thank you for painting a much clearer picture of the internal design of the IR Tower. I agree with your observations, but have a question: Is the processor in the IR Tower controllable (i.e. downloadable, like the RCX)? If it is, then there's (...) (23 years ago, 28-May-01, to lugnet.robotics)
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| | Re: Custom Firmware, IR Problems, and Dead RCXs (long)
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I'm hard pressed to understand why one would need to continually transmit from either the RCX or the tower? Data logging comes to mind, but there aren't many cases where there is a need for this. Listening can, of course, be done continously. The (...) (23 years ago, 29-May-01, to lugnet.robotics)
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| | Re: Custom Firmware, IR Problems, and Dead RCXs (long)
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(...) For what it's worth, it's not actually that bad. I don't know the specs on the NPN transistor, but I suspect 1.14A would kill it almost instantaneously. One important factor you've left out of this equation is the 9V battery itself. We often (...) (23 years ago, 29-May-01, to lugnet.robotics)
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| | Re: Custom Firmware, IR Problems, and Dead RCXs
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(...) Actually, it's the computer itself that determines the duty cycle. This does mean that you could change the duty cycle, but you should be aware that it would be at the expense of noise immunity and would require a higher sampling rate from the (...) (23 years ago, 29-May-01, to lugnet.robotics)
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| | RE: Custom Firmware, IR Problems, and Dead RCXs
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(...) Ummm, that doesn't make sense. You know where the midpoint is by knowing the baud rate, and hence the bit width. The only time you need to sample at the beginning of the bit time is to look for a start bit. This is all very basic asynchronous (...) (23 years ago, 29-May-01, to lugnet.robotics)
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| | RE: Custom Firmware, IR Problems, and Dead RCXs (long)
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(...) The use of alternative firmware such as pbForth, legOS and leJOS usually requires frequent upload/download cycles, and may use long communications periods. (...) I agree on this point, but that will affect the low power range more as well. (...) (23 years ago, 29-May-01, to lugnet.robotics)
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| | RE: Custom Firmware, IR Problems, and Dead RCXs
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(...) <snip> (...) <snipped more> Well, no. The RCX receiver is a standard IR unit tuned to the carrier frequency. when I look a the signal on my scope, I get a nice square-shaped wave that is the same as the data byte (with start and stop bits) (...) (23 years ago, 29-May-01, to lugnet.robotics)
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| | Re: Custom Firmware, IR Problems, and Dead RCXs (long)
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I don't understand all the problems about blown IR-LEDs and don't believe anyone will ever see 1A flowing through his IR-LED's. My experience: I'm doing contiunuous data transfers for hours in long range mode, with fresh batteries I measure 100 mA (...) (23 years ago, 29-May-01, to lugnet.robotics)
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| | Re: Custom Firmware, IR Problems, and Dead RCXs (long)
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(...) Oops. I just assumed that the RMS vs Peak value of an AC transformer and the subsequent consequences for the tower were so obvious that anyone with an electronics background would have pointed it out, and since you didn't, I figured you must (...) (23 years ago, 30-May-01, to lugnet.robotics)
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| | Re: Custom Firmware, IR Problems, and Dead RCXs
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(...) Gee, could you tell I don't have a block diagram of the innards of the RCX? 95% of the work I've done with microcontrollers has been based on the MC68HC705J1A, J2A and K1 series (mainly because that's what I have the development tools for). (...) (23 years ago, 30-May-01, to lugnet.robotics)
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| | Re: Custom Firmware, IR Problems, and Dead RCXs (long)
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Another way of working around the high power and range problems would be an IR repeater. Usually these are used to extend the range of IR remote controls to another room or to a stage. (URL) two-way device might be needed here -- I've also seen some (...) (23 years ago, 30-May-01, to lugnet.robotics)
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| | Re: Custom Firmware, IR Problems, and Dead RCXs (long)
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In lugnet.robotics, Matthias Jetleb writes: <snip...> (...) One important point that I haven't seen mentioned here is that the RCX AC adaptor input is labelled "9-12V~", which is AC, not DC. I have used the transformer that comes with the 9V train (...) (23 years ago, 30-May-01, to lugnet.robotics)
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