Hi, Marcus, Thanks a lot for your quick reply! Then start from where, the integers become floating point numbers? I'd like to see how they are converted.
Thanks, Yooxi Marcus D. Leech wrote: > > On 08/15/2011 01:22 PM, xi yang wrote: >> Hi, Tom, >> >> Thanks a lot for your prompt reply! >> Do you mean on the Transmitting side? >> I want to know how 32-bit floating point number is converted to 16bits >> or from 16bits to 32bits. >> Where can I find the file that performs this conversion? >> >> We are actually working on the Receiving side. >> Before we move I/Q samples from rx_buffer to USB, we want to do FFT >> and deliver the FFT results instead of the raw I/Q samples to the host. >> For my FPGA FFT module, I use 32bits floating point numbers as input. >> So I want to know how the I/Q samples are represented by 16bits so >> that I can convert them to 32bits. >> In 32bits representation, bits 0 through 22 form the mantissa, bits 23 >> through 30 form the exponent, and bit 31 is the sign bit. >> In 16bits, do we simply cut 16bits of the mantissa? >> Then bits 0 through 6 form the mantissa, bits7 through 14 form the >> exponent,and bit 15 is the sign bit. Is that right? >> It's better if we can have a look at the conversion file. >> Thanks, >> Yooxi >> > The host interface uses 16-bit integers for I and Q. They're only > represented as floating-point numbers within a Gnu Radio flow-graph. > > Internally in the FPGA, everything is integers, starting with 12-bit > integers from the ADC (on the USRP1), then through the CIC decimators > and DDC, they become larger, but what is finally injected into the > host is 16-bit (integer) I and 16-bit (integer) Q. > Standard twos-complement representation for the integers, I don't > happen to recall off the top of my head whether they're "big endian" > or "little endian". > > > > > > > -- > Marcus Leech > Principal Investigator > Shirleys Bay Radio Astronomy Consortium > http://www.sbrac.org > > > > _______________________________________________ > Discuss-gnuradio mailing list > [email protected] > https://lists.gnu.org/mailman/listinfo/discuss-gnuradio > > -- View this message in context: http://old.nabble.com/The-format-of-I-Q-sample-tp32262153p32266070.html Sent from the GnuRadio mailing list archive at Nabble.com. _______________________________________________ Discuss-gnuradio mailing list [email protected] https://lists.gnu.org/mailman/listinfo/discuss-gnuradio
