9 Channels With One Module on 9XR Pro?

[BLT]

The documentation shows adding a second TX module for transmitting
greater than 8 channels with the 9XR Pro.

But can it be done with one module?

On my old 9XR (non Pro), you could just select 12 channels in the radio
setup and it would control all 12 channels of the OrangeRX R1220X recievers.
But on my new 9XR Pro, selecting 12 channels does not help.
I can only get it to control 8 channels. Is there a setting that I have missed?

Why does the newer transmitter have less capability?

[MikeB]

If you can control 12 channels on the 9XR, then the 'PRO should be able to do the same. Perhaps post all the settings you are using on the 9XR for the protocol (PPM?) and those of the 'PRO.

Mike.

[BLT]

On the old 9XR (non Pro) in the first page of Model Setup, there's a setting for "Proto". There are several choices, the default being: "PPM 8CH 300uS". You can change the 8CH to 10CH or 12CH, but it doesn't make channels 9 and above work. But if you change the protocol to "PPM16 12CH 300uS" channels 9 through 12 work fine.

On the new 9XR Pro, there are only 3 choices for protocol, PPM, PXX and DSM2. No PPM16. Again,changing the PPM to 10CH or 12CH still does not allow channels 9 and up to work. And since there is no PPM16 option, channels 9 and up never work. My 9XR Pro has the ersky9x - r204 firmware.

Can anyone explain how channels 9 and up work in more detail?

Thanks!

[MikeB]

Curious. PPM16 is a special mode where (normally) you send 8 channels to the normal module, and 8 out on the Trainer port to a second module to get 16 channels. The normal module output works the same in PPM and PPM16 modes.
The reason PPM16 is not present on the 'PRO is it has a second PPM output (PPM2) available internally to provide an output to a second module.

What Tx module(s) are you using?

Mike.

[BLT]

I have the OrangeRX DSMX / DSM2 transmitter module. In my tests, I used the same module in both the 9XR and 9XR Pro radios.

I thought changing the PPM setting to "12CH" was supposed to allow 12 channels to fit into the standard PPM frame. But is this possible? How long is the frame and how long is each channel? And what is the "300uS"? Perhaps the spacing between the channels?

I also noticed a setting for PPM Frame whose default was 22.5mS. What exactly is that? I tried reducing and increasing that, but it didn't seem to help in getting channels 9 and above to work. I only need channels 9-12, not 13-16.

[jhsa]

Can the orange module output 12 channels?

João

[MikeB]

A PPM frame contains all the channel pulses and a 'sync.' pulse. The start of each pulse is generated by a short pulse of about 300uS, the actual value you may set. Rather than being a space between channels, this is actually included in each pulse.
Each channel is normally 1 to 2 mS long. The sync. pulse is then the rest of the frame length that has the default length of 22.5 mS.

So, for 8 channels, the channels pulses could take upto 16 mS, leaving 6.5mS for the sync. pulse. From experiments I've done I would recommend making sure the sync. pulse is at least 4.5 mS long.
For 12 channels you need a frame length of at least 12*2 + 4.5 = 28.5mS. I would try setting the frame length to 29 or 30 mS if you use 12 channels.
If you enable "extended limits", then each channel could be longer than 2mS, actually up to 2.14mS, so you would then need a little more on the total frame length.

Mike.

[BLT]

Don't you need a delay time between the channel pulses too?
Isn't that the 300uS that's specified in the protocol (PPM 8CH 300uS)?
Or am I mixed up here?

So for 8 channels: 8 X (2 + .3) = 18.4 plus 4.1 for the sync pulse gave 22.5mS.

The PPM16 worked because it was set to "12CH". Probably more channels were being sent out on the trainer port but they were 13 and up so I saw no effect.

When changing the protocol and frame width, I found out that you need to restart the TX and RX for the settings to take effect. That explained my erratic results earlier.

Through extensive trial and error experimentation, I think I have this figured out. This is what I found:

12 channels with one TX module works perfectly on both the 9XR and the 9XR Pro if you change these 2 settings in the first page of the model setup and restart both the TX and RX:

1) Set the Protocol to PPM 12CH 300uS
2) Change the PPM Frame length to 30mS

[MikeB]

The 300uS is included as part of each channel, it isn't extra. So, if a channel pulse is 1.2mS, get a rising edge, 300uS a falling edge, then 900uS after that the rising edge at the start of the next pulse. 300+900 is 1200, the channel pulse width.
Normally, you don't need to restart the Tx to change the the PPM output, perhaps your Tx module picks up there are 8 channels then doesn't adjust if 12 are sent to it until it is powered off and on. I hae monitored the PPM output on an oscilloscope and seent the number of channels and the frame length change as you adjust the settings.

Mike.