Download PWM to PPM converter

PWM to PPM converter
This converter was designed to support PPM signal to MNAV. Modern 2.4 GHz RC
receivers don’t have PPM output so converter devices have to be used to generate it.
This converter was designed for Futaba R608FS receiver but it can be used with any 8
channel receiver.
Schematic:
Description:
The microcontroller captures every PWM channels and generates the PPM signal.
The input signals are connected to resistor ladders (R21-R36). Value of these resistors
should be chosen according to the signal level of the receiver. Sum of value of ladder
elements should be around 10 Kohm. PWM signal of Futaba R608FS has 3 V amplitude
so R22 R24 R26 R28 R30 R32 R34 R36 aren’t used.
The PPM signal is connected to PIN46. It was configured as an open drain output with a
4,7 Kohm pull up resistor. Supply voltage: max 5 V.
There is a LED on the board which is blinking during normal operation.
PIN out:
GND
NC
PPM Signal
ICSP
Servo CH1-CH8
Receiver CH1-CH3
NC
Receiver CH8
GND
+5V Receiver CH4-CH7
+5V
GND
Converter with receiver:
Notes:
Channel 8 is unimplemented by the firmware of the controller. Value of channel 8
remains constant on the PPM signal. If channel 8 is necessary firmware modification has
to be done. After the modification channel 8 have to be connected with a separate servo
cable.
If the noise of supply voltage is grater then 500 mVP-P following things should be done:
Support 5 V supply on not connected pin of PPM connector.
Break the supply line of LM1117
Connect PIN3 of LM1117 with PIN2 of PPM connector.
Unsolder pull up resistor of the PPM output.
Solder a new pull up resistor between PPM output and PIN2 of the PPM
connector