A/D then D/A question

[zabuun]

Hi,

I'm a newbie to A/D operation.

Let's say I want to use ADC0808. I have 8 single ended input and I connect 8 different analogue values to ADC0808. When I look at the output of ADC0808, I see that 8, 14, 15, 17, 18, 19, 20 and 21 pins are the outputs. The thing that I can't understand is the conversion. Let's say input values are ;

Channel 1 : 1.5 V
Channel 2 : 2.5 V
Channel 3 : 1.6 V
Channel 4 : 2.4 V
Channel 5 : 1.2 V
Channel 6 : 2.2 V
Channel 7 : 1.3 V
Channel 8 : 2.3 V

After 8 bit conversion is done, for my knowledge, I have 8 bit values (e.g., 00100110 for channel 1, 00100110 for channel 5, etc.) for each channel. But there is only one 8 bit output. I want to learn which channel's value I am reading at that moment.

Any help will be appreciated. I know my knowledge is not enough yet but I'm really trying to learn.

Thanks in advance,
Amuri

 

[ericgibbs]

hi,
Only 1 of the 8 possible inputs is selected by the 3 address bits.

So channel 0, Address 0,0,0 would select analog Input 0, after conversion the 8 parallel bits for Input 0, would appear on the output pins.

OK.?

 

[zabuun]

Hi ericgibbs,

Thanks for your quick reply.

So how can I see other inputs on output pins? How can I change the address of the input?

Best regards,
Amuri

 

[ericgibbs]

Hi ericgibbs,

Thanks for your quick reply.

So how can I see other inputs on output pins? How can I change the address of the input?

Best regards,
Amuri

hi,
You could use Bit switches to select the channels or a MCU.

A timing Clock and Start pulse is required, look at this datasheet. Page #2 shows the layout.

 

[zabuun]

Thanks a lot ericgibbs, I'll be working on it. If I have a question, I will ask again.

Best regards,
Amuri