Lpc2000

After getting a great deal of good advice from the group, here's my 
small contribution:

A simple example of how to use the LPC2138 to create a sine wave 
using direct digital synthesis (DDS).

It was developed for the Keil LPC2138 board and compiler and puts out 
an audio tone from the DAC using the amplifier on the board. It 
should work for other boards as well.

It's amazingly simple to create very nice looking sine waves using 
DDS on the LPC2138. The waves can easily be frequency modulated or 
amplitude modulated, and you can create musical chords by combining 
multiple sine waves.

I included a couple technical documents that explain the process in 
detail--as a result there are relatively few comments in the source 
code.

Tom Kreyche

Sorry, I forgot to mention it's in the "DDS" folder in the file 
section.


--- In lpc2000@yahoogroups.com, "tkreyche" <tkreyche@w...> wrote:
> 
> After getting a great deal of good advice from the group, here's my 
> small contribution:
> 
> A simple example of how to use the LPC2138 to create a sine wave 
> using direct digital synthesis (DDS).
> 
> It was developed for the Keil LPC2138 board and compiler and puts 
out 

> an audio tone from the DAC using the amplifier on the board. It 
> should work for other boards as well.
> 
> It's amazingly simple to create very nice looking sine waves using 
> DDS on the LPC2138. The waves can easily be frequency modulated or 
> amplitude modulated, and you can create musical chords by combining 
> multiple sine waves.
> 
> I included a couple technical documents that explain the process in 
> detail--as a result there are relatively few comments in the source 
> code.
> 
> Tom Kreyche

----- Original Message ----- 

From: "tkreyche" <tkreyche@...>
To: <lpc2000@yahoogroups.com>
Sent: Saturday, February 12, 2005 11:42 PM
Subject: [lpc2000] Sinewave Direct Digital Synthesis Example Posted


>
>
> After getting a great deal of good advice from the group, here's my
> small contribution:
>
> A simple example of how to use the LPC2138 to create a sine wave
> using direct digital synthesis (DDS).
>
> It was developed for the Keil LPC2138 board and compiler and puts out
> an audio tone from the DAC using the amplifier on the board. It
> should work for other boards as well.
>
> It's amazingly simple to create very nice looking sine waves using
> DDS on the LPC2138. The waves can easily be frequency modulated or
> amplitude modulated, and you can create musical chords by combining
> multiple sine waves.
>
> I included a couple technical documents that explain the process in
> detail--as a result there are relatively few comments in the source
> code.

I did something similar some time ago with the LPC2106, with an AD557 DAC. 
That was when I found the limitation on the GPIO speed, I couldn't generate 
a higher frequency than I could with an AVR.

Leon 



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> I did something similar some time ago with the LPC2106, with an 
AD557 DAC. 
> That was when I found the limitation on the GPIO speed, I couldn't 
generate 
> a higher frequency than I could with an AVR.
> 
> Leon 


Well, you're sure not going to implement a GHz digital radio, but 
it's fine for audio frequencies. I needed a fancy tone generator for 
a project -- it turns out to be damn near impossible to get the chip 
vendors who make melody ICs for cell phones to sell them in small 
quantities.

So for $5 the LPC2132 works well for audio (and you can play .wav 
files too).  If you slow it down the current is < 10 mA.

Tom