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Old Nov 13, 2012, 03:27 PM
Brandigan is offline
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Originally Posted by happul3 View Post
I may be missing something here, but the purpose of those links is to produce actual voltage on the low voltage side of shifter. It is essentially a cool trick - using unidirectional channels of voltage shifter, which are simple voltage dividers, to produce constant level voltage that is then used to pull up actual bidirectional shifters. If one believes the sparkfun schematic, in the drone 1 case the divider produces 5V*R5/(R1+R5)=2.5V and in the drone 2 case the divider produces 5V*(1/(1/R5+1/R9))/(R1+1/(1/R5+1/R9))=1.7V So, if you connect mod wired for drone 2 to drone 1, you'll be feeding drone 1 with logical high of no more than 1.7V. Is it high enough for 3.3V logic? I don't know, "They might or they might not," said Winnie-the- Pooh. "You never can tell with bees." But there is no harm in trying.
I measured 2.49v and 1.67v for the Pro Mini and 2.31v and 1.54v for the Nano before I fritzed the Nano, as they both started with different voltages: 5.01v and 4.63v respectively.

Well, it didn't work with LV>RX0 link still connected on the v1 drone but that's not the weirdest part...
Can't say it won't in the future, as I can't get it to work with a Level Shifter on a Pro Mini at all.

I moved the Level Shifter and it's connections from the now dead - but previously working - Nano to the Pro Mini, as that's working just fine with a v1 using resistors.

Only 6 wires. Easy.

It wouldn't startup on the v1. Removed the Level Shifter again, remade with Resistors - works on the v1 again - Swapped back to Level Shifter again - checking every connection - and the Mod gets to the end with a solid Arduino LED, but with Red Motor lights every time. Telnetted in, ps and ls /tmp show no sign of at2so.arm.

That was using a 'normal' sketch without the baudrate change. So tried again with that sketch, (after resoldering everything). No change. If I leave it for a while, the Arduino light starts flashing, then ls shows the directories followed by gibberish and then it loses the connection.

Swapped back to resistors again. Tada! Works perfectly.

So I just cannot get it to work with the Level Shifter and a Pro Mini, but it works with a Pro Mini and resistors, and a Level Shifter and a Nano (or used to). When I get another Nano, I will try it with both Level Shifters and their wiring 'looms' to see what result I get, as it's perfectly possible that I've fried both Level Shifters. However if either/both work with the new Nano....

So my questions are:
1) Are these Level Shifters particularly delicate?
2) Am I frying them when soldering them (the test for this will be when I try these with the new Nano)?
3) Has anyone got either a v1 or a v2 drone with Level Shifters to work with a Pro Mini, or is everyone using a Nano?
4) If the answer to 3) is 'yes' did you have any problems and how did you solve them?
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Last edited by Brandigan; Nov 13, 2012 at 03:38 PM.
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