Here comes my way to build the Mike Amp. first we have to realize that this Mike Amp. is probable more sophisticated than the one used commercially as it's fully programmable and can be adapt to almost any servo.
I show the board here running an old "Icon" that now can be flown again.
This picture shows necessary components, a DRV8838, an Arduino Pro Mini board and my "custom made stacking board connectors".
...and here I'm showing the wires connected to the 2 boards before and after mating.
To do this I have moved the ppmin from 2 to 6. I have also included my settings for the DIY
#define potRotation 180 //What the electrical movement of the servo/pot is
#define servoRotation 160 //What the total servo rotation is (must be equal or less than the pot rotation) for a 900uS to 2100uS ppm input
#define Kp 150 //The proportional gain for the error signal (
#define deadBand 10 //The servo dead band to stop the servo hunting for its set position in +/- uS /2
#define centre 0 //To adjust the centring of the servo, can be a +/-value eg -12 or 14. It's value is very roughly equivalent to +/-uS movement (1200/1024 = 1.17uS to be precise)
#define ppmIn 6 //must be in the range D0 - D7 (was ppmin 2)
#define drv8838EN 3 //must be in the range D0 - D7
#define drv8838PH 4 //must be in the range D0 - D7
#define potIn 0 //where the servo pot connects, must be in the range A0 - A7
This is how I build them and allows me to stack the DRV8838 on top of the Arduino.
One remarks, this will only work if voltage of 4,8v -5-2v is applied i.e. 4s NiMh or the regular output of 5.0-5.2 v from a speed control would do fine but anything else will probably damage it and release the "blue smoke" contained in some of the electronics - 2s LiFe is a No-No