Max 118 Adc

[niraj_khandekar]

hey guys, im working on this robotics project and im having sme problem with ma ADC.. they microcontroller when works fine and gives correct voltage at all the ports without the adc attached.. bt when i insert da ADc, all the ports go high showing 5 volts.. from what i interpretted from the datasheet, the conversion starts when WR goes frm high to low. (MODE 1). 4 bits are latchd, next four bits conv starts when wr goes frm low to high. int goes low when conv is finished. send low signal to rd for to access the data. ive programmed the controller accordingly, bt it doesnt seem to work.
plz help me out..
thanx..

 

[blueroomelectronics]

Consulting crystal ball, nope can't tell without a schematic or source code.

 

[rsnk]

Here is the datasheet for max 118 adc which is 8 channel 8 bit adc
View attachment adc datasheet.pdf

 

[Nigel Goodwin]

Why not just use a modern micro-controller with ADC built-in?.

If it doesn't work, then you probably haven't programmed your micro-controller correctly, but you haven't even mentioned what controller it might be, never mind posted the source code.

 

[rsnk]

We are familiar with using P89V51RD2 Philips 8051 micro controller, and it does not have a built in adc. So we need to use an external ADC.

status of control pins are as follows:
chip select , cs=gnd;
mod = vcc;(write-read mode)
power down, pwrdwn=vcc;

We used the following prog to interface the microcontroller wit our adc:

#include <P89V51RD2.h>
#define adc_port P2 //ADC Port
#define rd P3_5 //Read signal P1.0
#define wr P3_4 //Write signal P1.1
#define intr P3_6 //INTR signal P1.3
#define ref 0x0f
#define led P3_7
#define a0 P3_0
#define a1 P3_1
#define a2 P3_2

void conv(); //Start of conversion function
void read(); //Read ADC function

unsigned short int adc_val;

void main()
{

a0 = 0;
a1 = 1;
a2 = 1;
wr = 1;
rd = 1;
while(1){ //Forever loop
conv(); //Start conversion
read(); //Read ADC
if (adc_val>ref)
led = 1;
}
}

void conv(){

wr = 0;
wr = 1;

while(intr); //Wait for INTR to go low
}

void read(){
//Make CS low
rd = 0; //Make RD low
adc_val = adc_port; //Read ADC port
rd = 1; //Make RD high

}