Project Objective: Develop an open source AIS Alarm that alerts sailors that a new marine vessel with AIS is within range
In this post the dAISy receiver will be connected and the first AIS messages received.
The green LED on dAISy indicates an AIS message!
The dAISy receiver is easily accessible. A header is provided with RX, TX, GND, 5V, 3V3, and even RST and TST for the very brave. Here TX on dAISy has been connected to RX on the FR2111 prototype breadboard. The antenna is connected on the left bottom connection of dAISy and power is coming in on the right. Things worked too after I remembered to connect GND between dAISy and the prototype. Doh!
There is debug capability for dAISy available over the USB connection. By default the serial connection of dAISy on the header described above is inactive. The photo below shows a configuration window open in a terminal session and serial made active at 38400 baud. Don't forget to save the settings! All of this is explained in the dAISy manual.
And for those who want to see what AIS NMEA messages looks like, here they are streaming into the debug window:
Now it is time to see if the messages are being received properly by the prototype. Main() in the code was modified to check UART for incoming characters and store them into a temporary buffer called incoming. When the special character '\n' is detected then the message is complete and the message is placed into TX buffer of UART character by character.
int main(void) {
WDT_A_hold(WDT_A_BASE); // stop the watch dog
PMM_unlockLPM5(); // activate port settings after power on
initClocks();
initGPIO();
initTimerB0();
initUART();
__bis_SR_register(GIE); // globally enable interrupts
for(;;){
// Manage incoming NMEA sentences
static int i = 0; // tracks charachters read from UART
while (RXFlag == 1){ // read incoming chars
if (i < MSG_LEN-1){ // do not overrun temporary buffer *** How to handle error?
incoming[i] = (char) RXData; // store in temporary buffer
RXFlag = 0; // reset flag
}
incoming[++i] = 0; // store end of string at next location
if (incoming[i-1] == '\n'){ // newline indicates end of NMEA sentence
size_t length = strlen(incoming);
int j = 0;
for(j = 0; j < length; j++){
TXData = incoming[j];
EUSCI_A_UART_transmitData(EUSCI_A0_BASE, TXData);
while(EUSCI_A_UART_queryStatusFlags(EUSCI_A0_BASE,EUSCI_A_UART_BUSY)){
// Wait until complete
}
}
incoming[0] = 0; // reset temporary buffer
i = 0; // reset counter
}
}
}
}
The logic analyzer was set up to read both incoming and outgoing activity on the prototype. The entire incoming and outgoing NMEA messages from the prototype cannot be fit into one window in the logic analyzer and still be read. But the following screen shot shows the two sentences compressed and further checking shows a perfect match.
This is real progress. Now to set up the ring buffer and see if memory is looking sufficient to store the desired 16 messages.
Past Posts from this Project:
AIS Alarm - Prototype Hardware
AIS Alarm - Prototype Code Outline
References and Links:
WEGMATT LLC - dAISy AIS Receiver - low cost AIS receiver
Texas Instruments MSP430FR2xx FRAM Microcontrollers - Post No. 4