Technical > Schematics

Schematics for the RigPi Audio and RigPi Keyer boards can be downloaded through the following link:

RigPi Audio Circuit Description

The RigPi Audio board is based on the Cirrus Logic WM8731 (U1) low power stereo codec. It supports a stereo input and mono output. The left input and output channels are transformer isolated for hum reduction. Both stereo input channels are available for I/Q signal processing. This input path is not transformer isolated.

The WM8731 is controlled through the Raspberry Pi GPIO connector.

GPIO 1 (Pin 12) BCLK: Digital Audio Bit Clock, Pull Down,

GPIO 19 (Pin 35) LRC: DAC Sample Rate Left/Right Clock

GPIO 20 (Pin 38) ADCDAT: Digital data out

GPIO 21 (Pin 40) DACDAT: Digital data in

SDA (Pin 3) SDIN: 3-Wire MPU Data Input / 2-Wire MPU Data Input

SCL (pin 5) SCLK: 3-Wire MPU Clock Input / 2-Wire MPU Clock Input

The WM8731 can convert input data with up to a 96kb sample rate.

Additional GPIO pins used for RigPi Audio:

GPIO 17 (Pin 11): PTT

GPIO 27 (Pin 13) DS: Clock for KX3 Power On voltage doubler

GPIO 22 (Pin 15): KPTT: Toggle for KX3 Power On

Connectors:

J1: Raspberry Pi GPIO connector

J2: 3.5 mm jack for I/Q input (stereo, unisolated)

J3: 3.5 mm jack for left channel audio input (tip, transformer isolated)

J4: 3.5 mm jack for audio (tip), PTT (ring), and KX3 (ring) power on signal

J5: Connector to route audio to the RigPi jumper board

Jumpers:

JP1: KX3/PTT (1-2 for KX3 Power On pulse, 2-3 for normal PTT)

JP2: Audio In selection (1-2 for stereo -no transformer isolation-, 2-3 for left mono -transformer isolated- input)

Elecraft KX3 Power on circuit

Transistor Q1 inverts and buffers a clock from the GPIO connector to feed a voltage doubler diode pair, D3. Q2 turns on emitter follower, Q3, to supply a short 7-volt pulse to turn on a KX3 through the ring connector on the KX3 microphone input.

RigPi Keyer Circuit Description

The K1EL WinKeyer3 CW Keyer IC provides all of the programming for its many features. The keyer is controlled through the internal serial port on the Raspberry Pi, ttyS0.

RXD (Pin 8): Receive data (from keyer)

TXD (Pin 10): Transmit data (to keyer)

Connectors:

J201: Raspberry Pi GPIO connector

J202: 3.5 mm jack, PTT out (tip is PTT, ring is 5V pull-up)

J203: 3.5 mm jack, Paddle input (tip is DOT, ring is DASH)

J204: 3.5 mm keying output (tip keys, ring not used)

J205: speaker connection

J206: PB-NET (allows external switches to play back internal memory, not used)

J207: Programming connector, not used

Jumpers:

JP201: PTT enable (1-2 enables GPIO PTT, otherwise, GPIO PTT not used)

GPIO pins used for RigPi Keyer:

GPIO 9 (Pin 21): Data to radio keyer (only used at remote end)

GPIO 10 (Pin 19): Data from remote keyer (only used at radio end)

GPIO 17 (Pin 11): PTT

RXD (Pin 8): Receive data from keyer chip

TXD: (Pin 10): Transmit data to keyer chip