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Originally Posted by SiriusHardware
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may be putting > 3.3V into the RPi. And the PNP transistor doesn't really seem to be needed, as the 10k resistor in-series with +5V to it will be the limiting factor.
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I think we may both have been labouring under the same misapprehension Owen - the job of the R4 / T1 / T2 part of the circuit is to accept 0v/3V3 from the Pi (on the left) and supply 0V / 5V to the PET (On the right). So it's perfectly right that it takes its pullup from +5V through R4.
I think the circuit as drawn is probably fine, now that I am not looking at it cross-eyed. |
Yes, I understood it is just a 0/+3.3V to 0/+5.5V (inverting) level-converter.
- But using T1 PNP transistor, to form a complementary push-pull output stage, means you shouldn't need an RTL style Pull-up.
So it should have either R4 OR T1. Having both seems rather pointless, as the output source-current is still limited by R4!
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the (World's best selling Home Computer - around 30 million sold) C64 etc.
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Originally Posted by SiriusHardware
That record has apparently now been well and truly smashed by the Raspberry Pi.
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Yes, although it depends on if you classify the RPi module as a complete Home Computer (Although not much extra required - just Keyboard, mouse, monitor, PSU + Some firmware on an SD-card) , and you could buy a Starter kit with most of this).
But not sure if the Records-books have been updated, to the RPi yet.