Hello ,I am using esp32 to read mp3 from sd card and send sound wave (-65535 to 65535)to a blue tooth speaker.I am now able to send a 6s array :const unsigned char {0xFF,….really large};
But i now have to decode mp3 ged get each sound value ,convert it to hex(like 4000 to 0xFA0).but I don’t know how to do.I tried,and i got this message ,please help ,thank you.
Luke lin
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in this specific case, the code is assigning a c-string, array of chars, to a char, a single byte
char piano16bit_raw = "";
Thank you,I understand!
Thanks, could you give me a example to convert 256 to 0xFF in char?(But i tried to use char not const char but also failed)
not const char. piano16bit_raw needs to be an array of char either piano16bit_raw [] or *piano16bit_raw
consider
output
val 255, 0xff
code
byte val = 255;
char s [80];
sprintf (s, " val %d, 0x%02x", val, val);
Serial.println (s);
could you explan why i got output of:
val 255, 0xff
with this code?
Serial.begin(9600);
byte val = 255;
char s [80];
// sprintf (s, " val %d, 0x%02x", val, val);
Serial.println (s);
I don't know why char s has val in it
it's not
char c [80] =val
Thank you
luke
You are declaring the array in a function and not defining its contents hence it will contain whatever was already in the memory that the compiler allocates to it
Wow,could you tell me how to get only 0xFF Without "val,255"?
thank you
Luke
I am sorry but I don't understand the question
Is this really 17 bit sound?
all values in memory are binary bits. they can be represented in various ways. they could be pixels, they can represent integer numbers of floats. integer value can be represented in various ways, as binary, octal, hex or decimal.
sprintf() formats variables into the c-string, s array in various ways. "%d" means decimal. "%02x" mean 2 digit hexadecimal with leading zeroes.
Hi,I will do some calculations to make it from 0 to 256 thanks
Surely, you mean 0 to 255?
I did it ,this works:
Serial.begin(9600);
//int dat=216;
byte val = 216;
char s [80];
sprintf (s, " 0x%02x", val);
Serial.println (s);
Well, I have got c==“0xFF”
But some thing is wrong
Code
Serial.begin(9600);
//int dat=216;
int val = audio.interleaved[0];
char s [80];
sprintf (s, " 0x%02x", val);
Serial.println (s);
SoundData *data = new OneChannelSoundData(s, sizeof(s));
a2dp_source.write_data(data);//send wave data to BT speaker
warning:
invalid conversion from 'unsigned int' to 'ChannelInfo' [-fpermissive]
Please post the entire error listing, not a snippet.
Why? You should be able to. The full message is chopped off the screen.