avnish aggarwal
ok put into USB device mode attach headset to analog out use control panel to set MBED as default output adjtst speaker volume to get sound play music
Fork of
USBAUDIO_speaker
by 
Samuel Mokrani
main.cpp@5:6afa90233635, 2011-11-30 (annotated)
- Committer:
- samux
- Date:
- Wed Nov 30 16:20:19 2011 +0000
- Revision:
- 5:6afa90233635
- Parent:
- 3:41b10e311100
- Child:
- 6:c44d017f93de
Who changed what in which revision?
| User | Revision | Line number | New contents of line |
|---|---|---|---|
| samux | 3:41b10e311100 | 1 | // USBAudio speaker example |
| samux | 0:5176b3dfccd6 | 2 | |
| samux | 0:5176b3dfccd6 | 3 | #include "mbed.h" |
| samux | 0:5176b3dfccd6 | 4 | #include "USBAudio.h" |
| samux | 0:5176b3dfccd6 | 5 | |
| samux | 0:5176b3dfccd6 | 6 | Serial pc(USBTX, USBRX); |
| samux | 0:5176b3dfccd6 | 7 | |
| samux | 0:5176b3dfccd6 | 8 | // frequency: 48 kHz |
| samux | 0:5176b3dfccd6 | 9 | #define FREQ 48000 |
| samux | 0:5176b3dfccd6 | 10 | |
| samux | 0:5176b3dfccd6 | 11 | // 1 channel: mono |
| samux | 0:5176b3dfccd6 | 12 | #define NB_CHA 1 |
| samux | 0:5176b3dfccd6 | 13 | |
| samux | 0:5176b3dfccd6 | 14 | // length of an audio packet: each ms, we receive 48 * 16bits ->48 * 2 bytes. as there is one channel, the length will be 48 * 2 * 1 |
| samux | 2:c3edc567ae33 | 15 | #define AUDIO_LENGTH_PACKET 48 * 2 * 1 |
| samux | 0:5176b3dfccd6 | 16 | |
| samux | 0:5176b3dfccd6 | 17 | // USBAudio |
| samux | 0:5176b3dfccd6 | 18 | USBAudio audio(FREQ, NB_CHA, 0x7180, 0x7500); |
| samux | 0:5176b3dfccd6 | 19 | |
| samux | 0:5176b3dfccd6 | 20 | // speaker connected to the AnalogOut output. The audio stream received over USb will be sent to the speaker |
| samux | 0:5176b3dfccd6 | 21 | AnalogOut speaker(p18); |
| samux | 0:5176b3dfccd6 | 22 | |
| samux | 0:5176b3dfccd6 | 23 | // ticker to send data to the speaker at the good frequency |
| samux | 0:5176b3dfccd6 | 24 | Ticker tic; |
| samux | 0:5176b3dfccd6 | 25 | |
| samux | 1:0335b5c18618 | 26 | // buffer where will be store one audio packet (LENGTH_AUDIO_PACKET/2 because we are storing int16 and not uint8) |
| samux | 2:c3edc567ae33 | 27 | int16_t buf[AUDIO_LENGTH_PACKET/2]; |
| samux | 0:5176b3dfccd6 | 28 | |
| samux | 0:5176b3dfccd6 | 29 | // show if an audio packet is available |
| samux | 0:5176b3dfccd6 | 30 | volatile bool available = false; |
| samux | 0:5176b3dfccd6 | 31 | |
| samux | 0:5176b3dfccd6 | 32 | // index of the value which will be send to the speaker |
| samux | 0:5176b3dfccd6 | 33 | int index_buf = 0; |
| samux | 0:5176b3dfccd6 | 34 | |
| samux | 0:5176b3dfccd6 | 35 | // previous value sent to the speaker |
| samux | 0:5176b3dfccd6 | 36 | uint16_t p_val = 0; |
| samux | 0:5176b3dfccd6 | 37 | |
| samux | 0:5176b3dfccd6 | 38 | // function executed each 1/FREQ s |
| samux | 0:5176b3dfccd6 | 39 | void tic_handler() { |
| samux | 0:5176b3dfccd6 | 40 | float speaker_value; |
| samux | 0:5176b3dfccd6 | 41 | |
| samux | 0:5176b3dfccd6 | 42 | if (available) { |
| samux | 0:5176b3dfccd6 | 43 | //convert 2 bytes in float |
| samux | 1:0335b5c18618 | 44 | speaker_value = (float)(buf[index_buf]); |
| samux | 0:5176b3dfccd6 | 45 | |
| samux | 0:5176b3dfccd6 | 46 | // speaker_value between 0 and 65535 |
| samux | 0:5176b3dfccd6 | 47 | speaker_value += 32768.0; |
| samux | 0:5176b3dfccd6 | 48 | |
| samux | 0:5176b3dfccd6 | 49 | // adjust according to current volume |
| samux | 0:5176b3dfccd6 | 50 | speaker_value *= audio.getVolume(); |
| samux | 0:5176b3dfccd6 | 51 | |
| samux | 0:5176b3dfccd6 | 52 | // as two bytes has been read, we move the index of two bytes |
| samux | 1:0335b5c18618 | 53 | index_buf++; |
| samux | 0:5176b3dfccd6 | 54 | |
| samux | 0:5176b3dfccd6 | 55 | // if we have read all the buffer, no more data available |
| samux | 2:c3edc567ae33 | 56 | if (index_buf == AUDIO_LENGTH_PACKET/2) { |
| samux | 0:5176b3dfccd6 | 57 | index_buf = 0; |
| samux | 0:5176b3dfccd6 | 58 | available = false; |
| samux | 0:5176b3dfccd6 | 59 | } |
| samux | 0:5176b3dfccd6 | 60 | } else { |
| samux | 0:5176b3dfccd6 | 61 | speaker_value = p_val; |
| samux | 0:5176b3dfccd6 | 62 | } |
| samux | 0:5176b3dfccd6 | 63 | |
| samux | 0:5176b3dfccd6 | 64 | p_val = speaker_value; |
| samux | 0:5176b3dfccd6 | 65 | |
| samux | 0:5176b3dfccd6 | 66 | // send value to the speaker |
| samux | 0:5176b3dfccd6 | 67 | speaker.write_u16((uint16_t)speaker_value); |
| samux | 0:5176b3dfccd6 | 68 | } |
| samux | 0:5176b3dfccd6 | 69 | |
| samux | 0:5176b3dfccd6 | 70 | int main() { |
| samux | 0:5176b3dfccd6 | 71 | |
| samux | 0:5176b3dfccd6 | 72 | // attach a function executed each 1/FREQ s |
| samux | 0:5176b3dfccd6 | 73 | tic.attach_us(tic_handler, 1000000.0/(float)FREQ); |
| samux | 0:5176b3dfccd6 | 74 | |
| samux | 0:5176b3dfccd6 | 75 | while (1) { |
| samux | 0:5176b3dfccd6 | 76 | // read an audio packet |
| samux | 1:0335b5c18618 | 77 | audio.read((uint8_t *)buf); |
| samux | 0:5176b3dfccd6 | 78 | available = true; |
| samux | 0:5176b3dfccd6 | 79 | } |
| samux | 0:5176b3dfccd6 | 80 | } |