Hi guys,

Just got my M5Paper these days and was playing with it, measuring the power consumption, figuring out the best way to approach writing a low power application for it. I really love the form factor and the capabilities. Figured out how to send esp32 in deep sleep and wake it via touch gestures (using doze mode).

I disconnected the internal battery and connected a lab power supply (4.2V) and tested the calculator app (while idling - no touch events, no screen updates)

• 169 mA - with the default app
• 93 mA - with EPD power disabled

My question is: why does the EPD consume so much power (almost half!) while the screen is idle? I was expecting it to be close to nothing.
Do I have a defective unit? Or can this be optimized in the EPD driver?

You can check other GT9xx drivers like (http://read.pudn.com/downloads710/sourcecode/embedded/2849392/gt9xx.c__.htm).

I will need to play some more with it. I'll probably post here a link to my repo once I push the code.

could you please share how you managed to get down to 1.5 uA?

Turn off the mosfet that powers the ESP32 (M5.disableMainPower(); - https://github.com/m5stack/M5EPD/blob/main/src/M5EPD.h#L49). In this mode everything but the external RTC (BM8563) is powered off.

In order to wake up from this mode you either need to press the button on the side, or use the external RTC interrupt.
The M5 lib contains a few functions that do exactly this (setup the external RTC to wakeup the board in a few seconds): https://github.com/m5stack/M5EPD/blob/main/src/M5EPD.cpp#L133

Yes, it's pretty straight forward to power down the ESP32 completely and the power draw in that state is about 1.5 uA.

I did play around more with power down states and I managed to get a light sleep mode with fast wakeup from touch at around ~9mA.

I didn't get to play around with doze mode yet. I hope to get 1-2 mA when touch is in doze (gesture?) mode and ESP32 in deep sleep.

@tatar-andrei said in M5Paper EPD power consumption:

169 mA - with the default app
93 mA - with EPD power disabled

So it seems that sending IT8951 in standby mode results in

• 75mA power consumption.

Which is a bit weird given that EPD power disabled (GPIO 23) takes about 93mA... Maybe it sources some current from the GPIO pins?

Yeah, I also checked the schematic. When the main MOSFET is powered down, the only way to wake up the device automatically is via the RTC chip (alarm or timer interrupt) and without any previous state (unless written to FLASH/SD). This is a good way of shutting down the device completely.

But the power consumption is actually ok with the ESP32 in deep sleep and the touch in doze mode. This will not be a "months on a battery charge" kind of application.

However I'm also looking into intermediate lower power modes, that's why I'm investigating different modes of operation of the EPD. Unfortunately there's not much info on IT8951, only drivers written by others. I'll investigate the standby power mode.

710mW for a calculator app that is just waiting for user input seems ridiculous! I bet it could get down in the double digit (maybe even single digit!) mW.

Hi guys,

Just got my M5Paper these days and was playing with it, measuring the power consumption, figuring out the best way to approach writing a low power application for it. I really love the form factor and the capabilities. Figured out how to send esp32 in deep sleep and wake it via touch gestures (using doze mode).

I disconnected the internal battery and connected a lab power supply (4.2V) and tested the calculator app (while idling - no touch events, no screen updates)

• 169 mA - with the default app
• 93 mA - with EPD power disabled

My question is: why does the EPD consume so much power (almost half!) while the screen is idle? I was expecting it to be close to nothing.
Do I have a defective unit? Or can this be optimized in the EPD driver?