Quote:
Originally Posted by gripped
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Some of the instructions I've found seem to mention only connecting to the 3 serial pins, namely here
https://www.mobileread.com/forums/sh...90&postcount=1
Is this because the TTL-232RG-VREG1V8-WE USB TTL Serial Cable supply's it's own power from the USB ?
And in other instructions
https://www.mobileread.com/forums/sh...07&postcount=2
a fourth wire connect from TP1706 to V and a ground other than the next to RX & TX on the serial pinouts is used.
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A tad confused. Sorry if this is a dumb post but I'm willing to give it a go but not an electronics expert !
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Quote:
Originally Posted by gustavonow
I am as confused as you are, also planning to use a 3.3v board with a step-down board, but I can't seem to find out if you need to connect 3 wires or 4 wires.
If you do get an answer please let me know.
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It all depends on the USB to serial converter that you use.
DO NOT mix and match the directions from threads that use different parts, at least not unless you read carefully and do not let your eyes/mind just skip over words you don't recognize the usage of.
TP1706, External reference battery, the fourth wire - -
Read the data sheet giving the technical description of the USB to serial converter YOU ARE USING (ignore all / everything about any converter you ARE NOT USING).
Does it say that you can set the (serial) output voltage by applying a corresponding REFERENCE voltage?
Yes - that is what the 4th wire is used for, to supply a reference level to the serial output stage of the converter.
If no mention of being able to set the serial output voltage of the converter - then most likely it is not possible set it with an external reference (it would say so if it supported that feature).
No mention == no TP1706, or external reference battery, no fourth wire needed to pass a reference signal that neither exists or can be used.
If you are reading one of my threads / series of posts about using the Kindle serial port - each of which I wrote ARE COMPLETE in and of themselves. You don't have to go outside of what I wrote. If a 4th wire is needed for the part (identified by part number almost always with the data sheet attached to the post) I mention, then the connection choices for the 4th wire is included.
If a 4th wire is not needed, then I only write about and document 3 wires.
I do not mix documentation on using a 4 wire convertor and then only describe 3 of the 4 wire connections.
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How to do this serial port connection - -
1) Pick the post(s) and or thread you are going to follow.
(Use the Master Index (the: "Where do I start" sticky) to look up things written here about serial port use.)
2) Get the EXACT (no substitutions allowed) part(s) described.
3) Use them EXACTLY like described.
Find that you have zero unanswered questions and zero problems.
Start substituting parts, then you have to start substituting words in the directions until the part(s) and the words match up once again.
But you only have your self to question, your the one that got off the described path to success.