interfacing ADS1115

bjornj · Joined: 30 Apr 2009 Posts: 33

Hello

I have tried to interface the 16 bit AD converter ADS1115 with very little succes.
I only get ones, FF FF, when reading the chip.
I have used data from the quick start guide in texas instruments datasheet.
I recently put in some delays and start/stop conditions, but that didn't help either.
Perhaps somebody with experience in this can figure out what i'm doing wrong.

/Björn Johansson

(BASCOM-AVR version : 2.0.7.7 , Latest : 2.0.7.8 )

Evert :-) · Joined: 18 Feb 2005 Posts: 2156

Hi,

Try the 12cscan.bas example from your Bascom directory to test if the hardware is working fine and if the i2c address matching your settings.

EDC · Joined: 26 Mar 2014 Posts: 971

Is the 90s8515 really chip You want to run this code or maybe You have Mega8515 that need "m8515.dat"?
Why don`t You use some chip with TWI. Even on Atmega8 You can use $lib "I2c_twi.lib" and then use Portc.4 and Portc.5
With really old chip`s where I2C was not implemented because it is a Philips patent or when I2C pins are occuped then software I2C make sens.
You should consider using dedicated I2C pin of some newer chip.

bjornj · Joined: 30 Apr 2009 Posts: 33

Thanks.
I tried the scan program and the result was 144 or Hex90
just like i should.
perhaps I could modify the program and see if I get an ack
when reading from the ADS.

Duval JP · Joined: 22 Jun 2004 Posts: 1161 Location: France

you need 2R 4.7k pull up on the I2C lines
did you put them ?
jp

bjornj · Joined: 30 Apr 2009 Posts: 33

Yes, I have a ready made little pcb with the ADS soldered on it.
It has all the pullups and some filtering capacitors.
Also the oscilloscope shows fine pulses 2x8 at the scl line
and 2x high at ada line when reading msb and lsb.
I also tried to capture the ack when reading the chip
with the scan program but it never came.
result 255.
perhaps this is where the problem sits, or did I make a poor
modification of the program.

part of the modified scan program.

I2cstart

I2cwbyte 144
I2cwbyte 0

For B = 1 To 254 Step 2

I2cwbyte B
I2crbyte lbyte, ack
If Err = 0 Then
cls 'we got an ack
lcd "Slave at"
lowerline
lcd B," ";
End If
I2cstop 'free bus
Next
cls
lcd "end ";B
End

kimmi · Joined: 24 Feb 2006 Posts: 1922 Location: Denmark

Hi,

did you see datasheet

Write to Config register:
First byte: 0b10010000 (first 7-bit I2C address followed by a low read/write bit) (H90/H91 OK)

Second byte: 0b00000001 (points to Config register)
Third byte: 0b10000100 (MSB of the Config register to be written)
Fourth byte: 0b10000011 (LSB of the Config register to be written)

Write to Pointer register:
First byte: 0b10010000 (first 7-bit I2C address followed by a low read/write bit) (H90/H91 OK)
Second byte: 0b00000000 (points to Conversion register)

Read Conversion register:
First byte: 0b10010001 (first 7-bit I2C address followed by a high read/write bit)
Second byte: the ADS1113/4/5 response with the MSB of the Conversion register
Third byte: the ADS1113/4/5 response with the LSB of the Conversion register

Try code:

bjornj · Joined: 30 Apr 2009 Posts: 33

Thank you very much Kim.
Your example worked very well.
I compared it with my code and as far as I can see
the differens is that every read must be precded by a
I2Cstart and followed by a I2Cstop.
with that also my code worked.
Thanks again for all help
Björn

kimmi · Joined: 24 Feb 2006 Posts: 1922 Location: Denmark

Yes its the "repeated START" and the "Ack /Nack" that works for the ADS1115

datasheet pages 17/18