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Re: [Paparazzi-devel] Electrical connections with the Tiny and PPM Enco
Re: [Paparazzi-devel] Electrical connections with the Tiny and PPM Encoder Board
Wed, 14 Jul 2010 16:10:20 +1000
Sorry Ana, I just looked at the wiki again and now get the "RC
Receiver classix.jpg" reference. I never noticed SERV_RST and SERV_CLK
before, whoops :)
In the wiki, section "R/C Receiver Interface" (*) it says:
* ...3 wires to the receiver (power and PWM)
* Cut the PWM trace and route it...
* ...4 wires (Ground, PWM-in, PWM-out, Reset)...
Shouldn't it say "PPM" instead of "PWM"?
If this is not an error, then I'm clearly confused and now fear a Heisencrash.
(*) here http://paparazzi.enac.fr/wiki/Other_Hardware#R.2FC_Receiver_Interface
On Wed, Jul 14, 2010 at 12:31 PM, Chris Gough
> Hi Ana,
>> Another question, what is the PPM Encoder Board function? I don't have one,
>> and after reading about it in the other hardware section and looking for
>> something in the devel-list, I'm not sure I have understood.
> Let me explain; to make my explanation coherent, I'll start with
> background information that you probably already know.
> Many RC transmitters send a PPM signal through the air, which is
> received by the RC receiver then demultiplexed into multiple PWM
> signals (which branch out to each of the actuators in parrallel). The
> demultiplexing happens within the receiver, it's a black box with an
> antenna (airborn PPM input) at one end and a bunch of PWM outputs at
> the other.
> In a paparazzi system it is the autopilot that sends the PWM signals
> to the various actuators, not the RC receiver (how else could it
> control the vehicle?). In manual control mode, the autopilot passes
> the input from the receiver directly to the actuators (relatively
> unmolested). When the pilot is in the loop (semi-manual mode), the
> autopilot takes the receivers input into consideration, but decides
> for itself what to send to the actuators. In autonomous mode, the
> autopilot basically ignores what the receiver has to say (except for
> the channel dedicated to selecting control mode; the pilot is allways
> in command, even when she is not in control).
> The "normal" way to configure a Paparazzi system (with no PPM encoder
> board) is to hack into your RC receiver and intercept the PPM signal
> from the appropriate place on the circuit board, attach your own cable
> to carry PPM from the receiver. In other words, ignore the bunch of
> PWM outputs. The autopilot has a single PPM input, that's where the
> other end of the custom cable from the hacked RC receiver goes.
> The PPM encoder board is kind of back-the-front receiver. It has
> multiple PWM inputs, and a single PPM output. I don't like to hack
> into my receivers because I don't trust myself not to break them.
> Instead, I have a bunch of PWM cables (servo extension leads with
> severed female ends) that plug into the unmodified receiver as though
> they were normal servo leads. The other end of these cables (bare
> wires where the female ends used to be) are soldered to the
> appropriate places on the PPM encoder board. Then PPM encoder board
> takes it's multiple PWM inputs and makes a single PPM output
> (undemultiplexes? remultiplexes? encodes multiple PWM inputs to a
> single PPM output), which then feeds to the autopilot.
> If I was using RC equipment that didn't send PPM through the air (for
> example, PCM or some 2.4 GHz system), extracting PPM from a
> vivisectioned receiver might not even be possible. In this situation,
> something like a PPM encoder board is the only option.
> I can't make pictures right now, but if you still need them ask me on
> the weekend and take some and publish them in the Wiki.
> Chris Gough
>>It's said it
>> plugs into the servo output of a receiver(like another servo?), and then you
>> can connect from the Encoder Board to the Tiny? Is it a way of not modifying
>> the receiver? Is it powered directly or can it be powered by the BEC?
>> Does anyone have a picture showing how the wirings go from the receiver to
>> the board and finally the autopilot? Sorry, but I am not very used to this,
>> and it's difficult for me to understand it.
> On Tue, Jul 13, 2010 at 5:05 PM, Ana García <address@hidden> wrote:
>> I've been reading the latest posts. I also have doubts.
>> I have thought about connecting the RC receiver in the "RC Receiver
>> classix.jpg" way. I mean, with the servos connected to the receiver. This
>> way, the servos can be powered by my motor BEC(which is connected to the
>> receiver). Then, the connections between the receiver and the autopilot will
>> be only PPM_IN, SERV_RST, SERV_CLK. Am I right? Is it a good choice?
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