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ADS8332 channel select question

Irving Wang
Prodigy 20 points
Other Parts Discussed in Thread: ADS8332

Hi,
I have some problems for using ADS8332.
I want to use manual channel select and Auto trigger mode. How can I select channel 2?
I code somethings, but it is error.

First, I give the convst pin high.

Second, I send the 'write CFR' code: 0xE000.
Delay 16-clock(70ns).

Third, I send 0x2000 to select channel 2
Delay 16-clock(70ns).

Fourth, I send 0xD000 to read CFR.
Delay 16-clock(70ns).

Then, I give the convst pin low.
and write a while loop to determine the EOC pin, if EOC is LOW, start to get data.
and, give the convst pin high.

that's all,

The result I only get data from channel 0 (first channel).
I don't know that why is not from channel 2.
And the conv pin do I need to configure it?
Can you help me?

  • 0
    TI__Mastermind 35450 points
    Hi Irving,
    Your channel switch is not implemented correctly. The Manual Channel select with Auto-Trigger mode enabled is generally used when the continuous conversions from a single channel are desired. In this mode, changing the channel requires that conversions are halted by setting the converter to Manual-Trigger mode. When the proper input channel is selected, the converter can be placed back to Auto-Trigger mode to continue the continuous conversions from the new channel.
    Auto-Trigger mode doesn't need /CONVST pin's involvement.

    Regards
    Dale Li
  • 0 in reply to Dale Li
    Prodigy 20 points

    Hi Dale,
    So you mean that I need to use the Manual-Trigger with Manual Channel select? Don't use the Auto-Trigger mode?
    I need to write one more Configuration before I send 0xD000 to read CFR?
    Or I need to write 0xE200, not 0xE000?

    If i delete the conv pin configurations in first step and last step, the result will be wrong(65535,65535,65535,65535.... 


    Actually, I want to use 2 channels to get data.( ch1, ch2, ch1, ch2etc)
    So I want to know how to select channel.
    would you give me some ideas?
    thanks !
    :)

  • 0 in reply to Irving Wang
    TI__Mastermind 35450 points

    Hi Irving,

    You can use Manual Channel select with Auto-Trigger mode, but if you want to switch the channel, you should set to Manual-Trigger mode. After switching the channel, you can go back to Auto-Trigger mode for continuous conversion. Auto-Triger mode is desired for continuous conversions from a single channel, it's better for your application to use Manual channel and Manual-Trigger mode.

    If really want to use Manual Channel select with Auto-Trigger mode, these steps can be used:

    1.  0xE6FF (Select Manual-Trigger,also disable Power-Down for test purpose)

    2. 0x2000  (Select channel 2, 3rd channel)

    3. 0xE4FF (Back to Auto-Trigger mode)

    4. 0xD000 to get data   (Figure 2 timing, first data isn't available when reading  during converting)

    Regards

    Dale