Shun SKNN

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9 years, 8 months ago.

How to use light sensor on FRDM-K22F?

FRDM-K22F has a visible light sensor - ALS-PT19-315C/L177/TR8 - as one of onboard sensors. How can I read value of it? What is its pin name?

Some pin names are shown in those documents: - ADC0_DP3 in http://developer.mbed.org/platforms/FRDM-K22F/ - ADC0_DP3/ADC0_SE3 in http://developer.mbed.org/media/uploads/sam_grove/frdm-k22f_sch.pdf - A0P3 in https://developer.mbed.org/media/uploads/mareikeFSL/frdm-k1_rev_1.3.pdf - Nothing in User's Guide http://developer.mbed.org/media/uploads/sam_grove/frdmk22fug.pdf

But I cannot find out any definitions of such pin names in the source code (PinNames.h for K22F): https://developer.mbed.org/users/mbed_official/code/mbed-src/file/01cb89f68337/targets/hal/TARGET_Freescale/TARGET_KPSDK_MCUS/TARGET_K22F/PinNames.h

Question relating to:

Last updated: 30 Jun 2020
The FRDM-K22F is an ultra-low-cost development platform for Kinetis K Series K2x (K22F) MCUs built on ARM® Cortex™-M4 processor. Features include easy access to MCU I/O, battery-ready, low-power operation, a …

I'm also hoping to see some code ;)

posted by Mickey Leroy 28 Mar 2015

For example, I wrote a simple code like this:

#include "mbed.h"

AnalogIn light(ADC0_DP3);

int main()
{
    while (true) {
        printf("Current value of the Visible light sensor: %f\r\n", light.read());
        wait(0.5);
    }
}

But I got an error:

Quote:

Error: Identifier "ADC0_DP3" is undefined in "main.cpp", Line: 3, Col: 16

The pinname "ADC0_DP3" came from pin layout. I think "ADC0_DP3" should be defined in PinNames.h...

posted by Shun SKNN 28 Mar 2015

When I jumper ADC0_DP3 and A0, I can read values via A0. /media/uploads/sknn/original_rps20150329_022139.jpg 

#include "mbed.h"

AnalogIn light(A0);

int main()
{
    while (true) {
        printf("Current value of the Visible light sensor: %f\r\n", light.read());
        wait(0.5);
    }
}

Value decreases while I put my hand over the sensor.

/media/uploads/sknn/k22f_lightsensor.jpg

This result shows that the light sensor is working but I cannot get its value via ADC0_DP3.

posted by Shun SKNN 28 Mar 2015

2 Answers

Fabrizio Fabrizio
9 years ago.

Hi there,

AnalogIn light(ADC1_DP0);

I can confirm that does not work.

Would it be possible to know where is the source file where pin names are defined?

thanks fabrizio

Mickey Leroy
9 years, 7 months ago.

Hey Shun, checkout the schematic file -> on page 5 you'll see the Visible light sensor... it's ADC1_DP0 / ADC0_DP3 Let me know how it works out!

Thank you for your comment. I've tried "ADC1_DP0" and "ADC0_DP3" in the source code shown above but I always get a same error. Aren't they pinnames?

posted by Shun SKNN 28 Mar 2015