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I need help using TLC548 or TLC549 serial ADC from Texas...

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mcoster

mcoster

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8051 and tlc549

Hi, i was wondering if anyone has used those ADC and could help me.

I have problem understanding how to use this ADC.

I think i did what they said in timing diagrams and operation theory but i dont get a stable reading. For example, if i am measuring 2.5 V i get reading in the 2.0 V to 3.2 V range ? Is this normal in serial ADC ? I don´t think so.
So i am asking for help.

Here is what i am doing.

CS = 0

Wait a little (2 us)

I do 8 clock cicles (to get out the previous data and start the hold operation)

CS = 1

Wait a little

CS = 0

Get the first bit (msb)

clock

Get the second bit

clock

and go on until the eigth bit

Clock

CS = 1



Thanks for your help
mcoster
 

1. Are you sure about your clocking? The ADC0831 requires 9 Clocks tog et the 8 bits, I do not know about your ADC timing, I'll check it later.

2. Are you sure you have a stable reference voltage?
 

Re: I need help using TLC548 or TLC549 serial ADC from Texas

Hi, first thanks for your reply.

I have a steady reference voltage. This is ok

According to what i could understand from the datasheet, this is what i should do:

When i bring CS to low, the MSB goes out

The next seven clock cicles gets out the other bits from the previus sample

And i need an eigth clock cicle to start another sample period

Thats what i could get

Thx, mcoster
 

After the CS = LOW, MSB goes out, then you will give the next pulse, at the Falling Edge of the next pulse, you will get BIT6 (MSB is BIT7 and LSB is BIT0). Then you will repeat this until clock 7, at clock 7's falling edge, you wwill receive the LSB or BIT 0, on your 8th clock's falling edge, you must put CS = HIGH, meaning your ADC will be disabled now, then you can put CS to LOW again and start the same method above.

I hope you are not getting errors due to a bug on your software.
 

Re: I need help using TLC548 or TLC549 serial ADC from Texas

I can confirm that TCL1549 and TLC1543 works very very well, for me.
The procedure You uses is ok.... first you must sample and convert data, then you can read it.
I've only ASM routines suitable for 8051 core... if you need, I can provide those routines here.
Bye. Paolo
 

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