ESP8266 Community Forum

- Tue Jun 09, 2015 11:06 am #19942 I was searching for some way of having something similar to the CC3xxx from TI that could connect to a previously configured AP very fast when exiting from sleep mode, avoiding to spare some seconds of battery power making the AP association. I didn't use the CC3000 before but saw that it can send messages using an AP a few milliseconds after exiting sleep. Is it possible to do this with the ESP8266?

Thanks!

Fernando

- Wed Jun 10, 2015 11:20 am #20065 Unfortunately I don't know the code to help you but this link might be an interesting read.

http://bbs.espressif.com/viewtopic.php?f=6&t=133

The sleep mode you describe sounds like Light Sleep, where it stays associated to the AP in a low power mode and can come back to life extremely fast.

If you are making a device that runs on batteries however that might not be best and you might need to enter a deep sleep and reactivate the device on a less regular basis.

It all depends on what you are doing, how big your battery is and how long you want it to last between charges.

If you find any code to enter Light Sleep would love to see it.

- Fri Jun 12, 2015 6:31 am #20250 Hi MHeys

Thanks for your reply! I'll check the information you sent me. Just for reference you can check the characteristics of the CC3000 in the LSR module power guide application note:

http://www.lsr.com/downloads/products/330-0099.pdf

In chapter 3.5 we can see the fast auto-connect timing, possible only if the AP profile is already stored in the CC3000. It takes about 780ms for being able to transmit (but I've seen references to shorter times in TI forum). This is what I want to check if it is possible to do with the ESP8266 (fast auto connect).

Fernando

- Sun Sep 04, 2016 6:49 pm #54476 Hi,

I have a similar question.
I want to save as much battery as possible.

I work with arduino, package 2.3 Basically it takes 3.5 seconds to connect to wifi and post to http.

I thought that much of the time was lost for wifi scanning, discovering, and dhcp negotation.

first I set IP as static with WiFi.config() => 1 second saved.
Then I added two arguments to WiFi.begin() : channel, and access point mac address :
now it take 450ms to connect to AP, 200ms to resolve server address and post (about half if you bypass DNS using server's IP)

Is there a "standard" way to tell to ESP to store last channel/bssid, and try first this before scanning?

If no, my idea is to code that. In my scenario, I'll have a single access point (one mac, one channel)