I had designed a remote unit for my ST4000+ autopilot. It did prove out the concept and I used it a lot, but it sported an unsightly coil cord (and of course unsightly coil cords have no place on boats) so I decided to build a wireless remote. The system (handheld Tx unit and stationary Rx unit) is based on a pair of microcontrollers and a pair of 433MHz radios.
The keypad/transmitter is on the left. It consists of a PIC16F628 microcontroller, Parallax 433MHz transmitter module ( and antenna, and membrane keypad built into the plastic box. It’s powered by a 9V battery. Power saving firmward allows it to run continuously for several months…there is no power switch. The receiver is on the right (above.) It consists of a Parallax 433MHz receiver module and antenna, PIC16F628 microcontroller, and Seatalk interface components. Schematic and firmware details are below.
Code:
/****************************************************************************
seatalk_wireless_remote_tx_1.c
This program is a remote control transmitter that sends a RxCx
number in an eight-byte message sentence with checksum.
Message protocol to the wireless receiver
* Each 9600 baud message contains a command and checksum:
0xff // wake up the transmitter and receiver
0xff // wake up the transmitter and receiver
0xff // wake up the transmitter and receiver
'J' // character
'S' // character
'F' // character
cMsgCode // which key was pressed
'J' + 'S' + 'F' + cMsgCode // equals checksum
+5
|
14
----------
R4 ----6-| B0 A0 |-17-- out to Parallax 433MHz transmitter
R3 ----7-| B1 A1 |-18-- out to LED
R2 ----8-| B2 |
R1 ----9-| B3 |
C3 ---13-| B7 |
C2 ---12-| B6 |
C1 ---11-| B5 |
| |
10MHz XTAL-15-| 16F628 |
XTAL-16-| |
----------
5
|
Gnd
KEYBOARD ASSIGNMENTS
C1 C2 C3
+------------------------+
R1 | (cable here) |
| |
R2 | |
| |
R3 | |
| |
R4 | |
+------------------------+
***************************************************************************/
For more detail: WIRELESS REMOTE CONTROL for Raymarine ST4000 Autopilot using PIC16F628
