Spektrum pulse setup for DM8 module?

[drigotti]

I'm using a Spektrum DM8 (not DM9) on a 3 channel proportional retrofit to 2.4. I'm using Phil's 7 channel sketch (Thanks Phil!) of course in a nano board. Looking over the values in the sketch I can see where to change the channel output from either Futaba or JR. (I set it to "zero") as I'm using Spektrum receivers. What I also see ppm pulse at 300us. I know on my reed tx build the sketch uses 400us. Also I see neutralpulse of 1200us. Should this be 1500?
Also...this module uses plus ppm as opposed to my DM9 that uses minus ppm. Does this matter in this proportional application?

ANY other changes that I should look for?

Thanks as always!

Dave Rigotti

[Phil_G]

Hi Dave, its been a while since I used my DM8 so I rigged it up & checked, and yes, it has the same timing anomaly as the DM9. To make the necessary changes properly isnt a 2 minute edit as theres lots to change.
I would set the PPM pulse width to 400 then take a shortcut by subtracting 100 from each channel value just before the PPM output. The PPM polarity is ok for the DM8 without any changes. Another point is that the DM8 needs a fair bit of drive, I normally protect the PPM output with a 1k resistor but thats too much for the DM8 so I would use a schottky instead, like we used to do with the early Frsky modules.

I've decided to do an update to the 7ch when I have a spare evening, if you can wait I'll sort it properly then. Or for now you could use something with conventional timing like Frsky, or OrangeRx if you need DSM2/DSMX.

I dont want to change much as I think its the 7's simplicity that makes it popular, but I do want to take the polled PPM out and use the Reeduino's interrupt driven PPM, maybe add a timer or whatever, maybe a low battery warning, but it will never even come close to the complexity of Mike & Martins encoders. KISS!

Cheers
Phil

[drigotti]

Phil,
I'll look at it but can't be sure of what's what.
BTW..... removing the 1K resistor and using a BAT42 got the RF deck working.........

My analyser shows all channels working along with the throttle hold switch.
The rate and expo pots work well too!
Just waiting on the buzzers.......

Pics to follow when things get tidied up.

Thank You!

Dave Rigotti