CC1310: Light pulse counter

Rustem Avkhadiev

Part Number: CC1310

Hello!

I used cc1310 4x4 to count the led flashing. Here the part of my schema:

DIO_7 is always HIGH. DIO_6 used as GpioTrigger in Sensor Controller.

Then led near phototransistor K1 changes state from Off ("dark" period) to On ("light" period) Sensor Controller awakes, increases the pulse counter by 1 and goes to sleep again.

In "dark" period - power consumption is 1 uA (all ok), but in "light" period power consumption rises to 9 uA.

Can i decrease the current "outgoing" from DIO_7 (or other pin)? Or any idea how to count led flashing with 1 uA budget?

Flash frequency is less then 10 Hz.

over 7 years ago

0 TER over 7 years ago

TI__Guru**** 317180 points

When you are using a photodiode, this will start conduction when light is applied. So if you want to keep the average power consumption low you have to apply power to the sensor only when actually measuring.

0 Rustem Avkhadiev over 7 years ago in reply to TER

Genius 3550 points

I tried to do this. Then i wake up Sensor controller 20 times per second to apply power to the sensor, power consumption > 9 uA.

0 TER over 7 years ago in reply to Rustem Avkhadiev

TI__Guru**** 317180 points

How much does the photodiode draw in the on periode with exposed for light?

0 Rustem Avkhadiev over 7 years ago in reply to TER

Genius 3550 points

0.4 mA.
I use this phototransistor: KP-3216P3C
But power spent to Sensor controller wake up operation, not to phototransistor. I tried to disconnect phototransistor, and power consumption still > 9uA.

0 TER over 7 years ago in reply to Rustem Avkhadiev

TI__Guru**** 317180 points

Based on the numbers in www.ti.com/.../swra578.pdf I can't see how you should manage to wake up 20 times pr second and use 1 uA even if your sensor had no current draw.

0 Rustem Avkhadiev over 7 years ago in reply to TER

Genius 3550 points

That because i ask for advice, how to solve this problem without frequent wake up.

Then i used cc1310 DIO_1 as power source (without analog capability), current was > 100uA. With DIO_7 current decreases to 9 uA.

May be i have the way to solve this problem on Pin side?

0 TER over 7 years ago in reply to Rustem Avkhadiev

TI__Guru**** 317180 points

Back to the basics for a second:
If I understand you correctly the pulses are 10 Hz meaning that you have to sample with 20 Hz to ensure that you get all the pulses?

0 Rustem Avkhadiev over 7 years ago in reply to TER

Genius 3550 points

Yes, i need to sample with 20 Hz to catch all the pulses. "Dark" and "Light" periods are random but not less than 50 ms. Full cycle is random also, but not less than 100 ms.

0 TER over 7 years ago in reply to Rustem Avkhadiev

TI__Guru**** 317180 points

As the app note I linked to show, waking up 20 times pr second even without doing anything draws more current than your budget.

0 Rustem Avkhadiev over 7 years ago in reply to TER

Genius 3550 points

20Hz is a maximum frequency for short (random) periods. Average long term frequency is less than 1 Hz

0 TER over 7 years ago in reply to Rustem Avkhadiev

TI__Guru**** 317180 points

I assume since the periods are random that you always has to sample with 20 Hz to not to miss a pulse?

0 Rustem Avkhadiev over 7 years ago in reply to TER

Genius 3550 points

If i need to periodically check phototransistor state - yes, 20 Hz. But if i will just wait for GpioTrigger (like i do now), i do not need it.
I need to decrease the current "outgoing" from DIO_7.

0 Rustem Avkhadiev over 7 years ago in reply to TER

Genius 3550 points

Problem solved by adding RC chain after SensorPower

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CC1310: Light pulse counter