How to read ADC ADS7230 correctly

Hello Tom,

It's still NOT working for me.

I have some questions below

1) For configuration, I have ONLY one setup with

   1.a) Assert CS

   1.b) Send out 0xE4FD along with 16 clocks

   1.c) De-assert CS

2) For data read, I have tried 2 different ways :

   2.a) Single operation with ONLY one CS activatyion

      2.a.1) Assert CS

      2.a.2) Send out Channel_Id ( 0 or 1) with 4 clocks

      2.a.3) Capture Data Read with 12 clocks

      2.a.4) De-assert CS

 >>  I got data read 0 for both channels !?!?

   2.b) Two operation with 2 CS aqctivations

     2.b.1) Assert CS

      2.b.2) Send out Channel_Id ( 0 or 1) with 4 clocks

      2.b.3) De-assert CS

     2.b.4) Assert CS

      2.b.5) Capture Data Read with 12 clocks

      2.b.6) De-assert CS

 >>  I got data read 0x8000 for both channels !?!?

So, what's wrong with my procedure ?

Thanks, Tom

~Duy-Ky

Hi Duy-Ky,

What is happening with the EOC/INT pin?  The 0xE4FD you write to the CFR is setting the device up to do Manual Channel select and Auto Trigger mode with TAG disabled.  Try running with Manual Channel select and Manual CONVST instead, or Auto Channel and Auto Trigger.  How fast is your SCLK?  A scope shot of your control lines would be very helpful here as well.   

Hello Tom,

Per the schematic, the HW engineer left 2 pins opened : EOC and #CONVST

So, per datasheet, I guessed the conversion started once I send 4-bit channel number ?

Is there anything wrong with those 2 pins above ?

Thanks so much, Tom

~Duy-Ky

Hi Duy-Ku,

Is CONVST open or pulled high?  If you don't actively control CONVST, you force yourself to use Auto Trigger mode, in which case you should also use Auto Ch select with TAG enabled (see note1 under Table 1).  If CONVST is floating (open) this might be the cause of your frustration.  Please review Figure 3 in the data sheet - CONVST should be logic 1 (high) when using Auto Trigger mode.

Hello Tom,

Yes, we missed the pin CONVST.

Now the pin is tied DIRECTLY to +5V

Now I use data 0xCFFF to set config for Auto Trigger, Auto-Channel and TAG bit enable

I have the procedure below to read data

1) Assert CS

2) Send Read Cmd 0xD along with 4 clks

3) Read Data with 13 clks, extra clk for TAG bit

4) De-assert CS

It's still NOT working for me. For many read in a row, I still get the same data 0x0180, instead of switching from 1st channel to the 2nd one

This value of 0x0180 or 384 might be for input voltage 344 mV I measured, while the other channel is at 3 mV

So, what's wrong with my procedure

I attached my scope shot for your reference. It's a PDF, let me know if you're not able to get the file

Thanks so much, Tom

~Duy-Ky

6215.ADC ADS7230.pdf

Hi Duy-Ky,

What is the time scale in your scope plots?  Can you also describe how the BUSY output reacts?  Please note that you must send at least 17 SCLKs to get the TAG bit out of the ADS7230 device.  This is described in Table 6 on page 36 of the data sheet. 

Hi Tom,

 The timescale is 200 uS.

It works for me now with the setting 0x4FD, ie my very first setting

• Manual Channel,
• Auto-Trigger,
• no TAG bit

I have to do RESET first then take it out of reset in order to make it work properly

Thanks so much for your great support, Tom

~Duy-Ky

Great news Duy-Ky!

I'm happy to hear that you've got the issues resolved.  Let us know if there is anything else we can help out.

Hello Tom,

I still have problem with ADS7230.

Before the converted data did not stay with the right channel.

That problem is gone, but a new problem is the converted data are NOT matched with the measured voltage

Channel 0 : measured  402 mV -> read around 2352

Channel 1 : measured 396 mV -> read around 2176

The results are about more than 5 times than measurements. They are still not correct even I shift 2 bits (divide by 4) !?!?

What I did were

1) Tie CONVST directly to 5 V : Is it correct ?

2) Set config 0x4FD (Manual Channel, Internal CCLK, Auto Trigger, NO TAG bit

3) I tried both ways and got the same results

   3.a) Single operation : Set channel and read result : I have to do at least 3 times to get right result for right channel

    3.b) Two operation

         3.b.1) Set Channel first

         3.b.2) Send READ op 0xD and read data : I also have to do at least 3 times to get right data for right channel

Any idea what went wrong

Thanks, Tom

~Duy-Ky

Can I get updated screen captures and raw conversion data?

Hi Tom,

Attached is screen capture for Read Config as 0x04FD as expected in setting and 5 Reads of Channel 1 with measurement of about 396 mV, but read about 0x900 - 2304 mV

Thanks, Tom

~Duy-Ky

1185.ADC ADS7230a.pdf