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Forum: FPGA, VHDL & Verilog Upsampling of a received signal from UART


Author: Roger Swan (roger237)
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I have read in various literature books that the baud rate generator in 
a UART module should generate a signal whose sampling frequency is 
exactly 16 times the UART's designated baud rate.

For a 57600 baud rate, the sampling rate of the signal would therefore 
be => 16 x 57600 => 921600 samples per second, am i right?

Given that I would then need to multiply this signal by a carrier wave 
and then output it using a DAC (PMOD DA2) whose sampling rate is that of 
1000000 samples per second, would I need to up-sample this signal ?

Author: Lothar Miller (lkmiller) (Moderator)
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Roger Swan wrote:
> I have read in various literature books that the baud rate generator in
> a UART module should generate a signal whose sampling frequency is
> exactly 16 times the UART's designated baud rate.
And now the question: WHY? In my RS232 code there is no specific 
oversampling with a correlated rate, instead I simply wait a bit time to 
read in the next bit value. Given that, I oversample a 57k6Bd signal 
with e.g. 100MHz and thefore by a factor of nearly 1700...


> Given that I would then need to multiply this signal by a carrier wave
Again: Why? What is it good for to multiply a more or less randomly 
chosen internal signal with a carrier?

Author: Roger Swan (Guest)
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I am multiplying the received signal with the carrier since i need to 
modulate this signal for my project purpose. The question is, given that 
i am going to pass the modulated signal through a dac whose sampling 
rate is that of 1Msps would i have to upsample the signal received from 
uart before i do the modulation part?

Do you have any idea how i would get to know the sampling rate of the 
received signal from uart?

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