Project Objective: Develop an open source AIS Alarm that alerts sailors that a new marine vessel with AIS is within range


Over the weekend I modified the PCB design, submitted it for production, and started thinking about refactoring the firmware.  This post will show the new PCB design and outline some of the thinking that went into it.  A first pass at the state machine will also be introduced.


Here is a rendering of the new PCB that is now being manufactured:

dAISy Alarm PCB V0.2

The main changes are:

  • Removed the LED that was causing interferences with the side of the case completely.  I decided I could convey necessary information with blinks of different length rather than multiple LEDs - remains to be seen how well that will work.  Reduces BOM and cost.  I considered using SMD LEDs very seriously but in the end settled for the 5mm one used here because I wanted maximum brightness.
  • Moved the dAISy on the alarm board directly over the header on the radio.  Bought some short "Dupont" 0.1" headers and will try to connect the two boards that way rather than use ribbon cable.  Will tidy things up and make assembly easier but is a tight fit.  Somewhat more costly since they are non-standard headers.  This is something of an offshoot of the idea Gene suggested in my last post.
  • Moved the buzzer forward to remove interference and placed the programming header behind it.  The microcontroller is now closer to the radio which is undesirable.  Need to check if this materially reduces reception from the radio when the PCB comes back.


This is the simplified state machine both as a diagram and a table showing movement from one state to the next.  In the old design there were LEDs for on/off, alarm, and ship detected.  Now it is done with one LED.  This is probably close but I have to keep stopping myself from adding features (KISS).

State Machine Diagram

Next State Table

The V0.2 board should be back by the end of next week.


I found someone who is willing to test it and give feedback when I am comfortable with the prototype.  It is a person who has sailed the Pacific on a small boat and is interested in looking at it.


Past Posts from this Project:

AIS Alarm

AIS Alarm - The Process

AIS Alarm - Prototype Hardware

AIS Alarm - Timers and GPIO

AIS Alarm - Prototype Code Outline

AIS Alarm - UART

AIS Alarm - First AIS Messages

AIS Alarm - First FRAM Storage

AIS Alarm - Debouncing Momentary Button Switches

AIS Alarm - FRAM Ring Buffer

AIS Alarm - Schematic

AIS Alarm - PCB Version 0.1

AIS Alarm - PCB Version 0.1 Arrived


References and Links:

WEGMATT LLC - dAISy AIS Receiver - low cost AIS receiver

Texas Instruments MSP430FR2xx FRAM Microcontrollers - Post No. 4

TI MSP430FR2111

Maximize the Sound from a Buzzer