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I am currently using the ADS1015 as an external ADC for my infrared sensor with my Particle Electron microcontroller. I am using this external ADC so that my microcontroller can stay in sleep mode until it is triggered. Currently, my IR transistor takes readings from an IR LED that is constantly on. I would like drive my LED with PWM and have the external ADC only read on HIGH.

Is there an external ADC that can take readings based on a trigger so I can synchronize it with my LEDs PWM?

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  • \$\begingroup\$ Yes. Find an ADC that can be disabled and one with a SYNC input. It's not clear why you can't just ignore the ADC readings though since you don't seem to be concerned about ADC power consumption. \$\endgroup\$
    – DKNguyen
    Commented Oct 31, 2019 at 22:33
  • \$\begingroup\$ @DKNguyen I do care about the ADCs power consumption and want it to be as low power as possible. I cant ignore the ADC readings because I want to wake up my microcontroller if the sensor is triggered. \$\endgroup\$
    – Tapatio Sombrero
    Commented Oct 31, 2019 at 22:56
  • \$\begingroup\$ My intention was to say "why can't you just ignore the ADC readings you don't need". If your entire objective behind this question is to reduce ADC power consumption then yeah, you need to get an ADC with a disable or sleep function. You may not even need a SYNC. Also make sure to check how long it takes the ADC to wake up and provide a reading. \$\endgroup\$
    – DKNguyen
    Commented Oct 31, 2019 at 22:58
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    \$\begingroup\$ So you're not really asking for an ADC you can trigger individual samples with an ADC. You're asking for an ADC you can shut down? \$\endgroup\$
    – DKNguyen
    Commented Oct 31, 2019 at 23:05
  • \$\begingroup\$ I wasnt planning to shut the ADC down, just trigger individual samples. But the ADS1015 Im using does have both single shot and continuous modes. Maybe I can just power the ADS1015 on and off with the pwm cycle and take single readings? \$\endgroup\$
    – Tapatio Sombrero
    Commented Oct 31, 2019 at 23:47

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You should change your architecture some. There are plenty of MCUs that have A/D converters right on board. You can simply feed the triggering signal into the MCU to wake it up. When the MCU wakes up it enables the A/D to take a reading. When the reading has been processed the MCU disables the A/D converter again and puts itself back to sleep to await the next trigger.

This should eliminate the need for two separate chips with some slow serial data interface between them.

Unless there is some aspect that you have not told us about this would be a better overall solution.

There are some applications where a separate A/D may be needed such as very high resolution converter, or one that has to work at very very low noise levels where you isolate the converter from noisy digital circuits.

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    \$\begingroup\$ In fact, the STM32F205 used in the Particle Electron has three separate 12-bit ADCs and a total of 24 analog input channels. \$\endgroup\$
    – Dave Tweed
    Commented Nov 1, 2019 at 0:18
  • \$\begingroup\$ To save power, I am trying to keep the microcontroller in sleep mode until something triggers the sensor. The microcontroller cant take ADC readings in sleep mode so I use the low power external ADC to monitor the sensor until something triggers it to wake up the microcontroller. \$\endgroup\$
    – Tapatio Sombrero
    Commented Nov 1, 2019 at 17:54
  • \$\begingroup\$ @TapatioSombrero - your comment indicates that you did not understand my answer. The MCU does not make A/D readings till after a trigger takes it out of sleep. \$\endgroup\$
    – Michael Karas
    Commented Nov 1, 2019 at 18:56

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