Working with ADC128D818 12 bit ADC & system monitor

Paulvk · Joined: 28 Jul 2006 Posts: 1257 Location: SYDNEY

Now while working with the MAX1238/9 12 bit ADC and looking for low cost devices this one came up http://www.ti.com/product/adc128d818?qgpn=adc128d818

This is a very interesting device it is a 12bit 8 channel ADC like the max1239 (see other blog) but has other functions as well, it has a temperature sensor on the last channel, it has upper and lower limit registers for each channel which if exceeded cause an interrupt any of these can be masked if not wanted , it will continually monitor its channels comparing this with no work by the micro thus it can be set up to monitor a system with analog output sensors and interrupt the micro if an out off limits value occurs. All this in a low cost device for around $4 AU.
I intend using them in the tree linear power supplies I am rebuilding they will monitor current, voltage and temperature levels sending an interrupt to the AVR if they are exceeded.

Nine devices can be on the buss even though it only has A0 & A1 pins it achieves this by having them as tri-state LOW, HIGH & MID (half of supply voltage).

Not a lot of code yet but this reads the internal setting registers.

Regards Paul.

Paulvk · Joined: 28 Jul 2006 Posts: 1257 Location: SYDNEY

Step two write to the registers:

This code first reads the value in the interrupt mask register (0000_0000 default) then writes 1001_1001 to it then reads it again to see the value changed Note the reading of the register is for debug purposes not needed in final code.

Regards Paul.

Paulvk · Joined: 28 Jul 2006 Posts: 1257 Location: SYDNEY

Now that we can read and write to the chip we can get it working.

Since it can measure temperature we will read this value
Now first we must > 1: Enable startup of monitoring operations
Then >1: Continuous Conversion Mode
We set bit 0 in register H00 to 1 then bit 0 in reg H07 to 1 after this we read the value from reg H27 this will be the temperature value in TWO's Compliment Note that "I2creceive &H3B , Vtemp" the variable Vtemp is an Integer because Bascom stores integers as TWO's Compliment thus Bascom will convert it to a number in normal human form for us!

Now that we have the chip working telling us the temperature it is now only a matter of writing values to the other registers and reading the converted values from the others.

See in the tables below for involved registers and note the order in which you program registers as the chip must be in shutdown mode to program some.

Regards Paul.