Reedino Red Board Question

[waynew17]

The modification to the Red Board for the Reeduino shows a wire strap and a PPM diode or resistor. Would somebody please clarify which option is best and the value or part number of the component. Thanks.

[Phil_G]

Hi wayne
The schottky diode was only necessary for the old Frsky V8 module which had no 5v protection on its 3.3v PPM input.
For all current modules, the encoder output can drive the RF module through a direct connection.
Cheers
Phil

[Mike_K]

Just to add too what Phil has said, you'll still need the schottky diode if you use a Futaba module such as a TM-7 FASST module, they expect to be driven by an open collector (switch to ground only) and having the schottky does the same. It's surprising how many people are still using old Futaba modules, I've had two support calls in the last few weeks about getting encoders to work with a TM-7 and a TM-8.

[waynew17]

I thought I was ready to perform the mods today and noticed my board is different than the Funduino labeled board. All of the pins and associated labels match on the top side of the board, but the bottom of the board has a different circuit layout. See photo. Sigh! The issue I have is that I'm not sure where to make the "cut" since my board is different. Have any of you had any experience with this version of the board or are able to determine where I need to make the cut?

[Phil_G]

Your board is clearly a different layout Wayne but the track must be on the 'top' side so if you could post a photo please we can see where.
The mod isnt essential, its just convenient. All it does is to remove 5v from the 5v pin to 'free it up' so it can be repurposed for battery voltage to power the RF module. Similarly the NC (no connection) hole is repurposed for PPM - again for convenience, not essential.
Or you could take the RF module pos straight from the on/off switch and take neg & PPM from the redboard D header (whichever one you used for PPM, initially with the redboard it was D13 but on later PCBs D0 was more convenient) Obviously the wiring has to agree with the sketch

By the way, beware of those solder splashes...

Okay: hard to be certain without a board in front of me [actually I found one and these assumptions are correct] but this is assuming the 5v doesnt go any further than the required pin.
Its the track on the very edge of the board, cut between the Vin & A0 legends.
If you make a narrow slot-cut it can always be bridged back again with solder.
After cutting the slot, test from the 5v hole to the reds of the headers - should be no continuity - but then test that all other 5v points are still connected together, ie all the red rows, & the Nano 5v pin. If all is well, solder the power input & RF module headers, & connect the Vin & 5v pins with a short loop, and the 'NC' pin to PPM, as per the document.

[waynew17]

Top of my Red Board attached:

[Martin]

It doesn't seem to do any harm, but that board also feeds 3.3V from its onboard regulator, to the Nano's 3.3V pin, which is supposed to be an output.
It's difficult to fix this 'fault' because the track swaps from top to bottom using the through hole in which the Nano's 3.3V pin sits. If you want to use the red board's 3.3V regulator to power the board's 3.3V header pins, and not have it powering the Nano's 3.3V output, the easiest option is to remove the 3.3V pin from the Nano itself; but that means modifying the Nano. The other option is to remove the 3.3V regulator from the red board, or cut the output track from the regulator, and the Nano then feeds the board's 3.3V header pins from its own regulator.
The Nano's own 3.3V regulator can't supply much current though - it's not as big as the one on the red board.

I modified mine, because I was connecting some components that drew quite a few mA from the 3.3V header pins, and I didn't want to overload the Nano's own regulator when I connected the Nano to USB, but didn't supply power to the red board's barrel jack.

[waynew17]

Phil,
Here's a photo of the Nano I plan on using. I believe this qualifies as an ordinary nano and will not require the 3.3V mod.

Thanks for your excellent instructions and especially your explanations. The explanations really help with the overall perspective since I am learning as I go.

Wayne, I have resized your photos to be less than 1 MiB each, please see PM Cheers, Tobe

[Phil_G]

Wow, not often you see a real one! It looks like a genuine Arduino (=expensive!) but for our purposes that is an 'ordinary' Nano and should be fine to use in the Redboard
The problem with documenting is (as you've discovered) that the available boards dont stay still, designs come & go, presently I'm struggling to find our beloved "DIY-More" board, but we'll get by one way or another Until your post I didnt realise the Redboards that James gave me were any different...
So, on with the project, keep us updated!

I've found the Redboards 3v3 puzzle to be odd but harmless on a standard Nano which only has the very low current 3v3 from the CH340G serial chip, but unsuitable for an RF Nano which has a proper AMS1117 regulator - with the two regs in parallel I found the RF Nano regulator gets hot.
I honestly think its a design flaw but can be ignored with an ordinary Nano, we've been flying redboards for years now!

By coincidence James (of Sticks & Tissue) recently gave me some Redboards, and looking at one they're the same as yours Wayne, outwardly they look the same as the Funduino but its a different track routing. Anywho, I had a shufty under the microscope, then cut the track suggested above, and can confirm all is well. When I get a mo I'll add it to the document although the use of Redboard is less common now.

Heres the track cut, between the annotations for Vin and A0. This frees the 5v pin to be used for power to the RF module - see the Reeduino doc.

So right to left these 5 pins are used as follows. two for battery power, and 3 (servo plug) for the RF module:

VIN - switched positive power from the battery (2S lipo etc)
G or GND - battery neg, a 2-pin JST socket will fit these 2 pins

G or GND - RF module neg
Vcc - this is the repurposed pin feeding battery voltage to the RF module via the short wire loop to VIN
NC - 'no connection' pin used for PPM, connected directly or via (say) a 1k resistor to Dn, whatever PPM output is used (usually D13 or D0)

RST - unused, no header pin fitted

[waynew17]

Phil:
Here's pics of my mostly completed Reeduino. Thanks again for all your help!!
Wayne