Lpc2000

--- In lpc2000@yahoogroups.com, Pablo Bleyer Kocik <pbk@e...> wrote:
> At 17:39 2004-02-20, you wrote:
> >I just recieved 3 pieces of the LPC2214FBD144 (144 pin part) from
> >philips as samples.  I was working on a rather complicated atmel
> >AT91RM9200 design with all the bells and whistles, but since these
> >parts arrived so quickly, I am considering putting that design on
> >hold for a bit and getting something actually working by using the
> >LPC2214.  Just to get something going, I am considering stripping 
my
> >design down to the following:
> >
> >LPC2214FBD144
> >2 channel 16 bit DAC on SPI #1
> >8 channel 8 bit DAC on SPI #2
> 
>   If this is for your laser controller, I would recommend parallel 
DACs. 
> You will have a bottleneck with SPI, and since you've got an 
external 
> memory interface, use that.

Yes, this is for a first run of the laser controller...sort of a get 
my feet wet thing.  Why should I have a bottleneck with SPI?  The DAC 
chip I want to use (TLV5630 if I just go all 12 bit, or TLV5632 if I 
go cheap and 8 bit) has a maximum SPI serial clock rate of 30mhz.  
The LPC2214 can operate its SPI at 1/8 of the pclk, or 7.5mhz for a 
60mhz clock from the PLL.  It takes 128 clock cycles to update all 
eight dacs which is 17.07uS.  Oh, ouch...the SPI data register is 
only 8 bits...thats a lot of cpu time just dinking with the 
registers....good point.  Too bad they didn't put a dma controller in 
the package.



> 
> >16 bit compact flash connector interface on the external memory
> >controller
> 
>   For true-ide? What kinds of cards do you plan to support? You 
don't need 
> the full CF bus for true-ide.
> 
> >RS485 level converter on UART0
> 
>   I guess this is for DMX512. Watch out for the break detection of 
the 
> USART controller.
> 
> >RS232 level converter on UART1
> 
>   MIDI? Or just plain RS232?
> 
> >output buffers for DACS (+/-10 volts on the 16 bit DACS, 0-5 volts 
on
> >the 8 bit, unless I find a 8 channel 8 bit dac with 0-5 volt 
buffers
> >built in)
> 
>   What kind of inputs has your laser? 8-bit DACs are typically 
> differential. The motor 16-bit DACs are usually both differential 
and bipolar.
> 
>   Have you considered an ILDA-compliant interface?
> 
> >Do you think this simple design is remotely possible on a 2 layer
> >board?  I would love to keep it at two layers for cost reasons.
> 
>   *Too* risky. To get the most of the 16-bit DACs, a ground plane 
is a 
> must. It saves a lot of headaches and layout time. Of course, 
always 
> separate your analog circuits from your digital signals.
> 
>   Regards.