mulitple lpc communication

cancel
Showing results for 
Show  only  | Search instead for 
Did you mean: 

mulitple lpc communication

231 Views
lpcware
NXP Employee
NXP Employee
Content originally posted in LPCWare by james on Tue Mar 27 20:10:14 MST 2012
Hi guys,

I need to measure an array of analog inputs, but my control board (lpc1768) only has 8adc, i am thinking of using multiples (>4) lpc1112 just as a another 8channel adc and transmit their signals via rs485. Anyone sees any potential catastrophic event for this setup?
0 Kudos
2 Replies

213 Views
lpcware
NXP Employee
NXP Employee
Content originally posted in LPCWare by Rob65 on Wed Mar 28 13:51:10 MST 2012

Quote: james
my control board (lpc1768) only has 8adc


Small correction: there is only one ADC.
It has an 8-fold mux that allows to perform up to 8 conversions of 8 different inputs but these are sequential conversions. If you need to sample the signals at exactly the same moment in time (e.g. when performing phase comparison) you need to use external sample&hold circuits.

This problem becomes 'worse' when using external multiplexers like Angelo suggests - it all depends on your application.
If these slight timing difference in sampling of your analog signals is not that important then I would indeed just use one of those muxes. Using multiple processors only makes life more complicated.

A 74hc4051 is way cheaper than the ADG408 so there must be a difference ...
Study the datasheets before making your choice.

Good hunting ;),[INDENT]Rob
[/INDENT]
0 Kudos

213 Views
lpcware
NXP Employee
NXP Employee
Content originally posted in LPCWare by Polux rsv on Wed Mar 28 06:08:14 MST 2012
add analog multiplexers before each LPC analog pin. For example, ADG408 is a 8to1 analog mux. If you put 8 ADG408, one for each AD pin, you could convert 64 channels in 8 burst conversions. You need 3 additional ouputs to drive the muxes. There are other analog multiplexers, CD4051, .... You should take care of power supplies and signals range. In other words, read the datasheets :D

Angelo
0 Kudos