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


Now that there is a working microcontroller that runs at the right clock speed and blinks a LED it is worthwhile to outline the firmware.

 * Outline of dAISy Alarm Prototype Code
void main(){
  initialize Clocks{
    32 kHz ACLK
  initialize GPIO{
    LED alarm
    Beeper alarm
    Serial RX
    Serial TX
    LED power
  initialize Timers{
    count milliSeconds
  initialize UART{
    38400 baud
  initialize Ring Buffer{
    16 messages of 120 bytes
    if display_button pushed{
      send all messages in buffer to UART TX
    if reset_tracking_button pushed{
      clear ring buffer
      initialize ring buffer
      turn off beeper alarm
      turn off LED alarm
    if (beeping == true) & (milliSeconds - startBeeping) > BeepLength){
      // beeps and LED toggle
      toggle GPIO LED alarm
      toggle GPIO Beeper alarm
    // manage incoming NMEA characters
    if (UART RX has character){
      store character in temporary buffer
   // end of NMEA sentence
   if last character read is '\n' {       
     store temporary buffer in the ring buffer
     clear temporary buffer
     start beeping
     start flashing the LED

If only writing real code were this easy.


It did flag something that should have put in the project description / specifications however.  The ring buffer is assumed to hold 16 incoming AIS NMEA messages.  The messages are less than 100 characters normally but the code will allow up to 120 characters to give some headroom.  Note that 16 messages of 120 characters is approximately 2k bytes.  The MSP430FR2111 only has 4k bytes of FRAM and that must also hold the program code.  In a pinch the number of messages could be reduced to 8.  In any event, the number of messages needs to be confirmed before the final design is started so if necessary a larger microcontroller can be substituted.


Past Posts from this Project:

AIS Alarm

AIS Alarm - The Process

AIS Alarm - Prototype Hardware

AIS Alarm - Timers and GPIO


References and Links:

WEGMATT LLC - dAISy AIS Receiver - low cost AIS receiver

Texas Instruments MSP430FR2xx FRAM Microcontrollers - Post No. 4

TI MSP430FR2111