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Comment by anthony_franco | Hacker News Reader

ESP32 development boards are also very impressive. And the prices are dropping every month. Can't wait to see that ecosystem evolve.

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Same goes for STM32 (ARM Cortex-M) hardware. Actually, the prices have already basically hit rock bottom. :) You can get a STM32F103C8T6 (72 MHz, 20 KB RAM / 64 KB flash) on a development board for under $5, and a programmer/debugger for about the same price.

ESP32 advantage is having 512 KB, back to the PC1512 days, just being multi-core and having network access. :)

And Espressif got their act together this time and are working on a good and open-source SDK (ESP-IDF).

I just tried it out this week to make battery powered wireless temperature and humidity sensors. Sleep current for the whole system is not that great (~80uA of which 40-50 are used by ESP32 module). However, the simplicity and ease of use outweigh having to charge the battery every 3 months (3Ah li-ion cell).

30-40uA with only the ULP running?

Now that you're asking- I don't really have an answer what exactly remains powered on. I have seen reports of people achieving sub-10uA sleep currents, so my result could be improved by a factor of 2 (LDO I put on board has Iq of ~40uA).

I haven't looked really deep at what power modes are available for each power/clock domain- at the moment I just have the ESP waking up from RTC timer every 15 minutes and it can also be woken up manually with GPIO. It's entirely possible that I have left some peripherals at non-optimal state.

I see. I haven't explored the low-power states yet, the datasheet says 5µA is possible using hibernation and timer-controlled periodic wakeup. Was curious if those numbers are achievable.

On the ESP8266 I was able to get down to 16.3 µA deep sleep current.

A lot of easy-to-use modules come with a USB-serial converter and a 5v-to-3.3v converter. These will draw a few microamps even when there's no USB connected - and depending on the precise hardware, some will draw far more than that.

You should plan on buying a few different modules and de-soldering a few components if you want to achieve the absolute minimum current consumption :)

I don't have any use for them, already enough side projects as it is, but the technical specifications of ESP32 are great.

It is like having a PC1512 that fits on the pocket, there are already lots of programming languages that would fit on it.

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