Author Topic: Is sleeping still worth it for frequent transmissions?  (Read 774 times)

Uncle Buzz

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Is sleeping still worth it for frequent transmissions?
« on: November 04, 2016, 12:54:34 PM »
Hi !
I'm wondering in which case I should put radio in sleep mode between 2 transmissions :
  • 50Hz (20 ms between 2 Tx)
  • 20Hz (50 ms between 2 Tx)
  • 10Hz (100 ms between 2 Tx)
  • 5Hz (200 ms between 2 Tx)
  • ...
How many time needs the radio to enter in sleep mode, and how many time to be ready to transmit again ?
I'm wondering only for the radio since I have some calulation at about 100Hz to do with the microcontroller...
Thanks for replies !

EDIT : thanks Felix for editing titile ^^, and I forgot to precise than I talk about RFM69HW
« Last Edit: November 04, 2016, 01:11:24 PM by Uncle Buzz »

Felix

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Re: Is sleeping still worth it for frequent transmissions?
« Reply #1 on: November 04, 2016, 01:11:36 PM »
You have to account that transmitting takes time, depends on your packet length. You should do some trials and measure the time, a good way is to use a logic analyzer and flip some IOs before/after a transmission. If you use ACKs that's roundtrips and retries, adds a lot more overhead.

You can always sleep between transmissions. But if you sleep 2ms and spend 18ms transmitting then you probably should look elsewhere for saving power more significantly.
My guess is if you transmit a LOT, then your power needs are very high compared to what you can save by sleeping a few ms in between transmissions.

perky

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Re: Is sleeping still worth it for frequent transmissions?
« Reply #2 on: November 04, 2016, 02:25:19 PM »
I and others have found issues with going into RX mode from standby, it appears not to fully reset the receiver even though the datasheet says it should, so the first packet due to be received after entering RX mode is lost. Subsequent packets are received OK. I suggest at least entering sleep just prior to putting into RX mode.
Mark.