Power Save vs Sleep?

[Fishbone69]

Hey All.
I am using an SH1106 and am able to get it to sleep and awaken using the u8g2.setPowerSave(1); I went back to the data sheet on the display and they discuss power save and also "sleep mode". Are power save and sleep mode the same thing? I am trying to use the lowest power consumption I can. So if sleep mode is less consumption than power save, I may want to look into that.

Thanks, smart ppl!

Fish

[olikraus]

The u8g2 power save cmd will usually only turn off the display. There are some rare cases where people contributed proper low power cmd sequence. In case of the SH1106 (which is compatible to the SSD1306) just the display is turned off:

u8g2/csrc/u8x8_d_ssd1306_128x64_noname.c

Lines 215 to 219 in b92f9e5

	static const uint8_t u8x8_d_ssd1306_128x64_noname_powersave1_seq[] = {
	U8X8_START_TRANSFER(), /* enable chip, delay is part of the transfer start */
	U8X8_C(0x0ae), /* display off */
	U8X8_END_TRANSFER(), /* disable chip */
	U8X8_END() /* end of sequence */

Things to consider:

• There are multiple ways to shutdown the display. There is a sleep mode (0x0ad cmd), but also a proper power down sequence including shutdown of the charge pump.
• There is a trade off between time and power consumption. Power up will take longer of the charge pump had been stopped.
• I could imagine, that full power down (display off, charge pump off) will be better then just sleep mode, but it probably needs to be measured.

[Fishbone69]

That seemed to have worked...BUT I got a very unexpected result. The FPS is about HALF of what I was getting on I2C. The I2C I was using HW vs SW but was running Full screen buffer mode on both.

[Fishbone69]

also, when putting the board to sleep I was using u8g2.setPowerSave(1);. Upon waking the screen doesn't come back on, even with u8g2.setPowerSave(0);

[Fishbone69]

lol...o.k. so when I go to HW with a reset pin, the performance SCREAMS
U8G2_SH1106_128X64_NONAME_F_4W_HW_SPI u8g2(U8G2_R0, /* cs=/ 7, / dc=/ 0, / reset=*/ 1);
I was getting 31 FPS with I2C. With SPI in SW I was getting 18 FPS. With SPI in HW I am getting 197 FPS!
However, I have used up all the gpio on my small board - it is a pico. I can recover 1 pin if I go with an SPI RTC and put it on the same bus. Also, any ideas on why it won't wake-up after powersave?

[Fishbone69]

o.k....I figured it out. The pin used for the clock on the SPI was previously identified as one of the wake pins. Everything works great now other than using up way more gpio pins. Thanks for all the help Oli. Do you have a place to donate to u8g2?

Fish

[olikraus]

I am happy that everything works 😃

[budger-collab]

Great question - this is exactly the kind of detail that matters when you’re optimizing for ultra-low power. Datasheets can be tricky, especially when “power save” and “sleep mode” sound similar but behave differently under the hood. Digging into how each mode handles internal clocks and refresh cycles is the right move. This mindset carries over to health too - people often ask how does inspire work for sleep apnea when they want a deeper, more efficient solution rather than just surface-level fixes.