hamster Posted November 21, 2012 Report Share Posted November 21, 2012 So I've just finished my latest project - an FPGA based FM transmitter that beeps out SOS in Morse code. All you need is a wire and 60 lines of VHDL!http://hamsterworks....ndex.php/FM_SOSI was musing over it all day and decided to give it a try.There I was feeling extra clever at how well it works, and upload the a video of it in operation to Youtube. As soon as it finished it recommends that I might want to watch another video - it is somebody transmitting music on FM using only an FPGA. I don't feel so clever now!This post has been promoted to an article Link to comment Share on other sites More sharing options...
Jack Gassett Posted November 21, 2012 Report Share Posted November 21, 2012 Well, I think it's pretty freaking clever, and useful too. It was pretty cool to see your yard over there in beautiful New Zealand. Oh, and I watched the other FM transmitter video, the guy had almost the same radio that you have too! Weird.Jack. Link to comment Share on other sites More sharing options...
jamesmount Posted August 30, 2013 Report Share Posted August 30, 2013 So I've just finished my latest project - an FPGA based FM transmitter that beeps out SOS in Morse code. All you need is a wire and 60 lines of VHDL!http://hamsterworks....ndex.php/FM_SOSI was musing over it all day and decided to give it a try.There I was feeling extra clever at how well it works, and upload the a video of it in operation to Youtube. As soon as it finished it recommends that I might want to watch another video - it is somebody transmitting music on FM using only an FPGA. I don't feel so clever now!This post has been promoted to an articleHello Hamster ! After seeing this device i am really confused, and i cant's give you any advice or solution related to FPGA based FM transmitter.But I have an question,why i used pulse width modulator (RFPWM) for transmitting the signal ? Link to comment Share on other sites More sharing options...
OmniTechnoMancer Posted August 30, 2013 Report Share Posted August 30, 2013 He isn't using PWM for transmitting the signal, he is using a numerically controlled oscillator to generate a square wave at RF frequency and adjusting it's frequency to produce FM. Link to comment Share on other sites More sharing options...
jamesmount Posted September 10, 2013 Report Share Posted September 10, 2013 According to my knowledge Square wave transmit by the help of code modulation. Then why we using PWM modulation. Link to comment Share on other sites More sharing options...
hamster Posted September 10, 2013 Author Report Share Posted September 10, 2013 The simple answer is it isn't using PWM - it is generating a signal that looks to be a 1 bit approximation of the FM signal. (i.e. if this was the desired signal would it be >0 at this point in time?) If you were to FFT the resulting signal you would have about 50% of the power at the desired frequency (which is what the FM radio can pick up), plus the rest of it is RF junk somehow related to the desired frequency and the FPGA clock frequencies. Link to comment Share on other sites More sharing options...
rafaelurquizo Posted September 13, 2013 Report Share Posted September 13, 2013 Good evening Mr Hamster The project is very interesting. I am a student and if u Could you help me?. I want to send audio. You said, audio with 16-bit resolution high quality mono. 1221381325 + / - 1.000.000 but I don´t understood very well that I add audio input in the process.,and what signal I use.This would be:if beep_counter(19) = '1' thenphase_accumulator <= phase_accumulator + 1222381325;elsephase_accumulator <= phase_accumulator + 1220381325;end if;elsephase_accumulator <= phase_accumulator + 1221381325; -- +/-1000000end if;This is my email: rafael_u_r@hotmail.esmy fpga is DE2-115 Cyclone IV and the audio codec is WM8731:Audio Codec, Signal name: AUD_ADCLRCK --Audio CODEC ADC LR ClockAUD_ADCDAT --Audio CODEC ADC DataAUD_DACLRCK --Audio CODEC DAC LR ClockAUD_DACDAT --Audio CODEC DAC DataAUD_XCK --Audio CODEC Chip ClockAUD_BCLK --Audio CODEC Bit-Stream Clock I2C_SCLK --I2CClockI2C_SDAT --I2CData My apologies if I ask too much, but it's a project, I'm doing at my university.I look forward to hearing from you soon.Yours sincerely Rafael Urquizo from Peru. Link to comment Share on other sites More sharing options...
hamster Posted September 13, 2013 Author Report Share Posted September 13, 2013 Hi Rafael, For a frequency I chose the modulation values used was something like 1221381325 +/-1000000, so when transmitting the positive side of the square wave I used 1222381325, and for the negative side I use 1220381325. This gives the required depth of frequency modulation (a frequency change of approximately 75kHz). If you have an audio stream of signed 16-bit samples A(n), You could use 1221381325 + 32 * A(n) for your modulation. Actually getting the values from A(n) from the CODEC is a different project! Link to comment Share on other sites More sharing options...
rafaelurquizo Posted September 30, 2013 Report Share Posted September 30, 2013 Dear Mr hámster.So, I could use the NIOS II program to configure the codec wm8731 records in "C", to obtain signed 16-bit samples A(n), I think so.And What more should know? Thank you!. your replies are very helpful me. Link to comment Share on other sites More sharing options...
hamster Posted September 30, 2013 Author Report Share Posted September 30, 2013 Not much more to know - you just add a 16 bit output port the NIOS II, and use that to tell the FM generator what freqency to generate... Link to comment Share on other sites More sharing options...
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