HDC3020-Q1: For the HDC3022-Q1 how quickly can one take Trigger-On Demand measurements?

Philip Weaver

Part Number: HDC3020-Q1

Under what conditions can one guarantee that an "Example Measurement Not Ready in Trigger-On Demand Mode" will never happen? Can one just pick a large enough time that "Example Measurement Not Ready in Trigger-On Demand Mode" will never happen? If so, how much time do I need to wait between measurements?

thx,

Phil Weaver

over 3 years ago

0 Pavani Deepthi Tenneti over 3 years ago

TI__Expert 3270 points

Hello Phil,

Thank you for posting to the Sensing Forum.

You can find the measurement duration on page 6 of the data sheet. This specification indicates the wait time required to read the temperature and humidity measurements. If you read a NACK after issuing a read command, you will have to wait a little longer in order for the conversions to be completed.

Regards,
Pavani Tenneti

0 Philip Weaver over 3 years ago in reply to Pavani Deepthi Tenneti

Prodigy 30 points

Hi!

When does the measurement duration start and when does it end? Will I always get a NACK after issuing the first read command after power up?

If I follow Figure 8-15 timing once per second, will I ever get a NACK after issuing the read command?

How many ms is "a little longer"?

thx!

Phil Weaver

0 Pavani Deepthi Tenneti over 3 years ago in reply to Philip Weaver

TI__Expert 3270 points

Hi Phil,

If you wait the recommended time, you will not see a NACK. 12ms is the typical measurement duration in the lowest power mode, which is what I would recommend as the wait time.

If you plan on measuring temperature and humidity every second, then I would suggest using the automatic measurement mode and configuring the device to read the values at 1 measurement per second.

Regards,
Pavani Tenneti

0 Philip Weaver over 3 years ago in reply to Pavani Deepthi Tenneti

Prodigy 30 points

Hi!

Why do you recommend automatic measurement mode? Automatic measurement mode seems more complicated than Trigger-On Demand mode. When does the measurement duration start and when does it end? Will I never get a NACK after issuing the first Trigger-On Demand read command after power up?

thx!

Phil

+1 Pavani Deepthi Tenneti over 3 years ago in reply to Philip Weaver

TI__Expert 3270 points

Hello,

The Automatic Measurement Mode performs a temperature and relative humidity measurement at a specific timing interval, removing the need for the I2C controller to repeatedly initiate a measurement acquisition. With trigger on demand, you will only obtain one measurement at a time and the device returns to sleep mode. Since you mentioned issuing the command every second in your previous reply, I suggested the AMM to ease the command structure.

The measurement duration begins right after the third ACK. You will need to wait the recommended duration after issuing this command in order to read the right temperature and humidity. Following these steps will result to an ACK every time.

Regards,
Pavani Tenneti

0 Philip Weaver over 3 years ago in reply to Pavani Deepthi Tenneti

Prodigy 30 points

Hi!

So, you are saying I can do a Write Command 0x2400 with a stop like Figure 8-3, wait 12 ms, and then issue a Read Multi Data Command like Figure 8-7 to get the Temperature and humidity data?

thx,

Phil

0 Pavani Deepthi Tenneti over 3 years ago in reply to Philip Weaver

TI__Expert 3270 points

Hi Phil,

With the Trigger on Demand command, you can only retrieve one set of temperature and humidity measurement.

Regards,
Pavani Tenneti

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HDC3020-Q1: For the HDC3022-Q1 how quickly can one take Trigger-On Demand measurements?