Lpc2000

Hi Brian, I've been using the 12-bit TI TLC2554 ADC (digikey stock) on
the LPC2106 SPI bus with good results. This LPC2106 code for this 4
channel ADC can run at over 80 KSPS when you've got the core clocked
at close to 60 MHz (using the PLL).  The part is capable of converting
at over 1 MSPS but the limitation in speed is due to the unbuffered
SPI bus on the LPC2100 series. In particular, the LPC2100 code in SPI
Master Mode has to send/recv the SPI data 8 bits at a time, but due to
the fact that some SPI transfers from the TLC2554 require up to
32-bits (multichannel mode) and most require 16 bits, the code has to
monitor the status and this slows things down a bit. I'm looking into
using a Xilinx Coolrunner-II to manage the SPI clock (= ADC clock) and
run the LPC2106 SPI in slave mode. 

Any one else have thoughts on the ADC SPI ?

Russ

--- In lpc2100@yahoogroups.com, "Brian C. Lane" <brian@s...> wrote:
> I'm working on designing a new project where we need to process 9600bps 
> packets (similar to G3RUH format), we'd like to use the LPC2106 which 
> ought to be fast enough. But I'm having trouble coming up with a 
> suitable  ADC. It needs to sample at 48khz, 10 bits are fine, 2 
> channels. It needs to be consistent (no jitter).
> 
> I could use a SPI ADC with the ARM as the SPI master, but I'm afraid 
> that other interrupts in the system will effect the sample accuracy (it 
> will also be doing some serial communications and have some timers 
> running) and introduce jitter into sample rate.
> 
> Ideally the ADC would be a SPI master with its own reference clock, 
> feeding the samples to the ARM with some indication (high bit 
> set/clear?) of which channel the data came from. There are some AKM 
> ADCs/codecs that might work, but their left/right clock would somehow 
> need to be associated with the data -- hard to do if you have a
delay in 
> getting to the interrupt to process the data and L/R has already 
> switched to the other channel.
> 
> Any thoughts?
> 
> Thanks,
> 
> Brian
> 
> -- 
> -----------------------------------------------------
> Brian C. Lane (W7BCL)                      Programmer
> www.shinemicro.com   RF, DSP & Microcontroller Design