Jamie Smith
Program to transmit strings as Morse code using the CC1200. Useful for amateur radio projects!
Dependencies: CC1200 SerialStream
This project contains a class (CC1200Morse) to convert text into Morse code that can be transmitted over a CC1200 radio IC, and a test program for this class. This is useful for amateur radio projects which need to broadcast their call sign in order to operate legally, and just a cool demonstration of the flexibility of the CC1200.
How It Works
First, the input string is translated into Morse code using a conversion table. Nearly all ASCII characters contained in the Morse character set are supported. For example, the string "ha" would become " ···· · −". Then, the Morse code is converted into one and zero bits according to the standard Morse timing rules. " ···· · −" then becomes 10101010 00010111 000". Finally, these bits are enqueued into the radio's packet buffer and transmitted. The CC1200 is configured into OOK (On-Off Keying) mode, so a 1 bit is modulated as full transmit power, and a 0 bit is modulated as zero transmit power. The transmission will occur at the speed (specified as the time unit, or the length of a dot) that you configure. Note that the CC1200 does the transmission in the background, so your processor can enqueue up to 128 bytes worth of Morse and then go do other things while it transmits at a human readable speed. You can't enqueue two packets at a time though.
Demo Video
Hardware Setup
This program assumes that a CC1200 radio is connected to your processor's SPI bus. The CC1200's circuit board must be configured for the 900MHz band (though you could also change the frequency in the code to match your boards).
I used a custom circuit board for my testing, but you should also be able to use an Mbed board connected to an CC1200 eval kit to run the program. Make sure to edit the #defines at the top of main.cpp to match the pins that your equipment is plugged into!
Note: License free transmission on the 900MHz band is only legal in Region 2 countries (North and South America). Make sure to follow all local regulations covering radio transmissions!
Diff: main.cpp
- Revision:
- 0:9e9ede3ac523
--- /dev/null Thu Jan 01 00:00:00 1970 +0000
+++ b/main.cpp Sat Aug 29 03:06:11 2020 -0700
@@ -0,0 +1,160 @@
+//
+// Test program for the CC1200 morse code example
+//
+
+#include <mbed.h>
+#include <SerialStream.h>
+
+#include <CC1200.h>
+#include <cinttypes>
+
+#include "CC1200Morse.h"
+
+#define PIN_SPI_MOSI P0_9
+#define PIN_SPI_MISO P0_8
+#define PIN_SPI_SCLK P0_7
+
+#define PIN_CC1200_CS P0_6
+#define PIN_CC1200_RST P0_29
+
+BufferedSerial serial(USBTX, USBRX, 115200);
+SerialStream<BufferedSerial> pc(serial);
+
+CC1200 radio(PIN_SPI_MOSI, PIN_SPI_MISO, PIN_SPI_SCLK, PIN_CC1200_CS, PIN_CC1200_RST, &pc);
+
+void testMorseCodeConversion()
+{
+ radio.begin();
+ CC1200Morse morseConverter(radio);
+
+ const size_t bufferLen = 64;
+ uint8_t outputBuffer[bufferLen];
+
+ char const * testString = "eternal silence@54!";
+
+ CC1200Morse::EncodedMorse morse = morseConverter.convertToMorse(testString, outputBuffer, bufferLen);
+
+ if(!morse.valid)
+ {
+ pc.printf("Morse is invalid\n");
+ }
+ else
+ {
+ pc.printf("Output %zu bytes:", morse.totalLength);
+ for(size_t index = 0; index < morse.totalLength; ++index)
+ {
+ pc.printf(" %" PRIx8, outputBuffer[index]);
+ }
+ pc.printf("\n");
+ }
+}
+
+/**
+ * Test sending some arbitrary bytes as OOK modulated data.
+ */
+void testMorseByteTransmission()
+{
+ const float timeUnit = 0.1f;
+
+ radio.begin();
+ CC1200Morse morseConverter(radio);
+ morseConverter.configure(CC1200::Band::BAND_820_960MHz, 915e6f, timeUnit, 14.5);
+
+ const char testString[] = "\xFF\x0E\xFF";
+ const size_t testStringLength = 3;
+
+ // manually create morse code data
+ CC1200Morse::EncodedMorse morse;
+ morse.valid = true;
+ morse.buffer = reinterpret_cast<uint8_t const *>(testString);
+ morse.byteLen = testStringLength;
+ morse.bitLen = 0;
+ morse.totalLength = testStringLength;
+
+ morseConverter.transmit(morse);
+
+ Timer messageTimer;
+ messageTimer.start();
+
+ radio.setOnTransmitState(CC1200::State::IDLE);
+ radio.startTX();
+
+ // wait until all bytes have been transmitted.
+ // Note: the FIFO length is 0 when the last byte is being sent, so we can't just check the FIFO length
+ while(radio.getTXFIFOLen() > 0 || radio.getState() != CC1200::State::IDLE)
+ {
+ pc.printf("TX FIFO size: %zu\n", radio.getTXFIFOLen());
+ ThisThread::sleep_for(std::chrono::milliseconds(static_cast<uint32_t>(timeUnit * 1000)));
+ //ThisThread::sleep_for(1ms);
+ }
+
+ float timeSeconds = std::chrono::duration_cast<std::chrono::duration<float>>(messageTimer.elapsed_time()).count();
+ size_t numBits = ((morse.byteLen * 8) + morse.bitLen);
+ float effectiveBitrate = numBits / timeSeconds;
+
+ pc.printf("Sent %zu bits in %.03f s, effective bitrate = %.03f sps\n", numBits, timeSeconds, effectiveBitrate);
+
+}
+
+void testMorseCodeTransmission()
+{
+ const float timeUnit = 0.1f;
+
+ radio.begin();
+ CC1200Morse morseConverter(radio);
+ morseConverter.configure(CC1200::Band::BAND_820_960MHz, 915e6f, timeUnit, 0);
+
+ const size_t bufferLen = 64;
+ uint8_t outputBuffer[bufferLen];
+
+ char const * testString = "eternal silence@54!";
+
+ CC1200Morse::EncodedMorse morse = morseConverter.convertToMorse(testString, outputBuffer, bufferLen);
+
+ if(!morse.valid)
+ {
+ pc.printf("Morse is invalid\n");
+ }
+
+ morseConverter.transmit(morse);
+
+ radio.setOnTransmitState(CC1200::State::IDLE);
+ radio.startTX();
+
+ // wait until all bytes have been transmitted.
+ // Note: the FIFO length is 0 when the last byte is being sent, so we can't just check the FIFO length
+ while(radio.getTXFIFOLen() > 0 || radio.getState() != CC1200::State::IDLE)
+ {
+ pc.printf("TX FIFO size: %zu\n", radio.getTXFIFOLen());
+ ThisThread::sleep_for(std::chrono::milliseconds(static_cast<uint32_t>(timeUnit * 1000)));
+ //ThisThread::sleep_for(1ms);
+ }
+}
+
+int main()
+{
+ pc.printf("\nCC1200 Morse Test Suite:\n");
+
+ while(1){
+ int test=-1;
+ //MENU. ADD AN OPTION FOR EACH TEST.
+ pc.printf("Select a test: \n");
+ pc.printf("1. Test converting to Morse code\n");
+ pc.printf("2. Test transmitting bytes as Morse\n");
+ pc.printf("3. Test transmitting string of Morse\n");
+
+ pc.scanf("%d", &test);
+ printf("Running test %d:\n\n", test);
+ //SWITCH. ADD A CASE FOR EACH TEST.
+ switch(test) {
+ case 1: testMorseCodeConversion(); break;
+ case 2: testMorseByteTransmission(); break;
+ case 3: testMorseCodeTransmission(); break;
+ default: pc.printf("Invalid test number. Please run again.\n"); continue;
+ }
+ pc.printf("done.\r\n");
+ }
+
+ return 0;
+
+}