Re: [Paparazzi-devel] PaparazziUAV project - control more servos

[Prof. Dr.-Ing. Heinrich Warmers]

Hi,
i think there are many  ways to a solution:

1 Cascade the 5-stage Johnson 4017b counter as described in the data 
sheet page 8  HEF4017B MSI 5-stage Johnson counter. You need a 
additional and gate like
   the   4081. This chip  has  four. (look  here aso 
http://www.dieelektronikerseite.de/Elements/4017%20-%20Der%20besondere%20Zaehler.htm.
   This solution may cause wrong pulses for one period of 40ms.
   Conneting the reset of the secound 4017b to the reset input of the 
first on the paparazzi autopilot  may solve this problem.
   You can also use a second free pin of the autopilot like the twog to 
reset the second counter.
   An disadvantage of the cascade solution is a  doubled time period to 
40 ms. This may cause problems with the  servos.

2 Use a additional counter to separate pins (reset, Impulse). With this 
solution you can generate a standard rate of 20 ms for all servos outputs.

3 For STM32 autopilots use 2 normal servo outputs for 2 4017 counters

4 Use the PCA 9685 with 16 outputs like this pcb  
https://www.adafruit.com/product/815 .
   You can cascade the pca9685 to get 32 outputs. This soulution will 
work with all paparazzi autopilots.


All this solutions need software changes. This may need same time to 
learn  the paparazzi software structures.

Regads

Heinrich







Am 10.10.2016 08:28, schrieb Ivan Fedorov:
>   Hi, 
>
>   My name is Ivan, I have an interest in  buinding RC
>   planes,  especially EDF jets. 
>   On this type of jets I typically have many control surfaces
>   you need to manage plus I need to manage thrust vectoring as
>   well. 
>
>   So typically I have many servos to manage (10+) with a
>   custom mixes from typical three control inputs (ailerons,
>   elevator, rudder).       
>
>   My intention is to build an on-board mixer which can take
>   these inputs from a receiver and  generate a feed for
>   multiple servos.   
>
>   I have been researcing what kind of hardware I can use for
>   that and your Lisa/S looks fantastic - small, lightweight
>   and expandable in case
>   I want to put more functions on it.   
>
>
>   However it only has a limited number of servos that it can
>   control. 
>
>
>   I wonder if it can be extended to control more servos using
>   an idea descrbed here 
> http://rcarduino.blogspot.com.au/2012/10/arduino-serial-servos-20-servos-4-pins.html
>
>   I would presume if I  take four of Lisa's output pins
>   to manage 2*4017 chips and add a relative small piece of
>   code to the PaparazziUAV project to control these pins
>   accordingly then Lisa could manage up to 20 servos. 
>
>
>   Could you kindly have a look to the URL above and assess the
>   idea?
>   Is that doable or there would be issues?
>   Where custom mixes can be configured?
> Could you please suggest what code blocks need to be written?
>
> I could try to develop them then and with your guidance add
>   to your project.   
>
>   Hope to hear from you soon.
>
>   Thank you and best regads, 
>   Ivan
>
>
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