MeekPE PPM Encoder Board

(PRELIMINARY)
MeekPE is a MCUless PPM Encoder.
This small board encode the PPM signal from the R/C receiver servo outputs without using any microcontroller.
Any type of R/C receiver is directly usable without any hardware modification.

Hardware Revision History

Version #	Release Date	Release Notes
v1.00	in progress...	0603/TSSOP PCB design
v0.10 (current)	08/2007	0805/SOIC Single layer test PCB design
v0.00	07/2010	Ugly Prototype

Features

• no MCU => no software
• up to 8 servo encoding inputs
• 25.4 x 15.6mm (1.0 x 0.6")
• ..g (..oz)

Prototypes

• 

  First ugly test (this is note a joke)

• 

  Test board 0805/SOIC components

Pinout

RECEIVER

Pin #	Name	Type	Description	Suggested Color
1	GND	PWR	Common ground	Black
2	+5V	PWR	5V to R/C receiver supply (optional, see connection instructions below)	Red or Orange
3 to 9	SERVO	IN	From R/C receiver servo output (see connection instructions below)	Yellow
10	LAST SERVO	IN	From R/C receiver servo output. Last channel to be encoded (see connection instructions below)	White

AUTOPILOT

Pin #	Name	Type	Description	Suggested Color
1	GND	PWR	Common ground	Black
2	+5V	PWR	5V rail from autopilot (see connection instructions below)	Red or Orange
3	PPM	OUT	Positive logic PPM output	Blue

Connections

MeekPE to Autopilot

Ground, Power ("+5V") and PPM signal must be connected to the autopilot.
Power ("+5V") pin is used to supply the MeekPE board (+3.5V to +16V) and can also supply your receiver. In this case, MeekPE supply voltage must match your R/C receiver power supply voltage (around +5V in general).
You can use a classic Molex 3 pin connector or solder wires directly on board: 3 additional bigger thru-hole pads are provided for this purpose.

R/C receiver to MeekPE

You can use a classic 0.1" pitch break away header and female/female jumper wires (like SparkFun's PRT-08430) or cut in half SparkFun's PRT-08430 female/female jumper wires and solder it directly to the MeekPe.

Powering the R/C receiver

• Ground connection is mandatory (voltage reference between the R/C receiver and the MeekPE encoder)
  
• Power output pin ("+5V") is used only if you decide to supply your receiver with the autopilot. In this case, MeekPE supply voltage from the A/P must match your R/C receiver power supply voltage (around +5V in general)

Servo connections rules

To get a correct PPM encoded signal, you must follow some (simple) rules:

• You must know the channel number of the first and the last servo signal you want to encode.
• All servo connection between the first and last channel you want to encode must be connected, even if you don't use it in the autopilot code.
• The last channel number servo signal you want to encode must be connected to the "LAST-SERVO" input pin of the MeekPE encoder. Other servos connections can be in any order because the channel encoding number is given by the transmitter, not by the MeekPE encoder.

Servo connection example

Ok, finally, servo connection rules are not so simple. So perhaps will it be better understandable with some examples.

• 6 channel receiver, you want to encode Throttle (channel#1), Pitch (channel#2), Roll (channel#3), and Mode Switch (channel#5):

=> connect #1, 2, 3, 4 R/C receiver servo output to any MeekPE servo input and servo R/C receiver servo output #5 on "LAST SERVO" MeekPE input. You can leave #6 unconnected.

• 8 channel receiver, you want to encode channel#2 to channel#5 and channel#7:

=> connect #2, 3, 4, 5, 6 R/C receiver servo output to any MeekPE servo input and servo R/C receiver servo output #7 on "LAST SERVO" MeekPE input. You can leave #8 unconnected.

Schematic

Assembly

Components Layout

• 

  MeekPE v1.00 Components Layout

• 

  MeekPE v1.00 Components Details

Bill Of Material

Qty	Manufacturer part #	Schematic part name / value	Designator	Description	Manufacturer	Package	Optional	Digikey.com	Other distributor
Resistors
8	RMCF0603FT1K00	1K	R1-R8	1/10W 1%	Stackpole	0603		RMCF0603FT1K00CT-ND
1	RMCF0603FT10K0	10K	R11	1/10W 1%	Stackpole	0603		RMCF0603FT10K0CT-ND
2	RMCF0603FT100K	100K	R9,R10	1/10W 1%	Stackpole	0603		RMCF0603FT100KCT-ND
Capacitors
1	?ref	10nF	C11	?spec	?man	0603		?dkref
8	?ref	100nF	C1-C8	?spec	?man	0603		?dkref
2	?ref	4.7uF	C9,C10	?spec	?man	0603		?dkref
Semiconductors
10	1PS79SB10	1PS79SB10	D1-D10	Schottky diode 0.2A/30v	NXP	SOD523 (EIA SC79)		1PS79SB10,115-ND
1	BC807-40	BC807	T1	PNP general purpose transistor	NXP	SOT23		568-1629-1-ND
Connectors
1	53047-0310	SRV0, SRV4, SRV2, SRV6, IRV, SRV3, SRV7	J12 to J18	Picoblade 3 pins 1.25mm straight header	Molex	specific		WM1732-ND