ADC problem on spartan3E
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From: John_H on 6 Jan 2010 15:40 On Jan 6, 2:18 pm, "mlajevar" <mahsa_lajeva...(a)yahoo.com> wrote: > > I got that the values on LEDs is the half of the value I expect from the > formula,so I think the problem would be with the 14th bit in my vhdl > code,because from 13th bit to LSB ,all bits are almost same,but the big > difference comes from being half of the original value caused by 14th > bit. Keep in mind that on a serial interface being off by a factor of two in your read value is the same as having the value off by one clock in the serial domain. Perhaps you're actually missing the least significant bit!
From: RCIngham on 7 Jan 2010 08:23
>On Jan 6, 2:18=A0pm, "mlajevar" <mahsa_lajeva...(a)yahoo.com> wrote: >> >> I got that the values on LEDs is the half of the value I expect from the >> formula,so I think the problem would be with the 14th bit in my vhdl >> code,because from 13th bit to LSB ,all bits are almost same,but the big >> difference comes from being half of the original value caused by 14th >> bit. > >Keep in mind that on a serial interface being off by a factor of two >in your read value is the same as having the value off by one clock in >the serial domain. Perhaps you're actually missing the least >significant bit! > From experience, this is an all-too-common problem with SPI and other serial interfaces... --------------------------------------- This message was sent using the comp.arch.fpga web interface on http://www.FPGARelated.com |