January 8, 2016
The ESP32
Originally this was an improved version of the infamous ESP8266 chip.
It still is I guess, but now there are more variants than I can keep
track of. One variant is the ESP32-C3, which has a Risc-V core.
I have a special section on it.
Here are some highlights of the original ESP32 (comparing to the ESP8266).
I'll just note in passing that the ESP8266 is still more than adequate for
most if not all things that I want to do.
- 520k of sram instead of 160K
- Runs at 160 Mhz (up to 240) instead of 80 by default
- Dual core Tensilica LX6 processor
- Bluetooth
- 28 (some say 36) gpio instead of 17
- 12 bit adc instead of 10 bit, and multiple channels.
- more uart, i2c, spi, etc.
- Temp sensor built in.
The CPU here is a dual core Xtensa LX6, whereas the ESP8266 had a single core Xtensa L106.
The clock frequency depends on the value of an external crystal (typically either 26 or 40 Mhz)
and is limited by the chip version. In general, the chip supports 240 Mhz, except for
ESP32-S0WD and ESP32-D2WD, which support only 160 Mhz).
The ESP32-S0WD is a single core version of the chip, and seems quite rare.
The extra SRAM is the biggest thing to my mind.
4 MB of Flash may be the same as the 8266 depending on what flash chip they ship with it.
Sparkfun ESP32 "Thing"
I tried to order several devices in late 2016, but my orders were cancelled after a long wait.
Sparkfun sent me the "thing" fairly promptly, but I only played with it briefly then and
lost interest in the ESP32 and left it laying in my drawer.
Note that the thing uses a 26 Mhz crystal. Many other devices use a 40 Mhz crystal.
Now in mid 2018, the supply seems to be quite ample and inexpensive devices are available from China.
You can get a bare "WROOM" module for about $4.50 now.
Development boards go for $7.50 and include a USB connector and USB to serial chip.
The WeMOS board (see below) is still available, but is just one of many options.
Adafruit Feather ESP32
Adafruit is cranking out a myriad of different feather boards. The ESP32 "Huzzah" seems to be the one of
interest if you are an ESP32 fan. It has LiPo support like the Sparkfun thing. The main attraction might
be the USB to serial chip that supports very high baud rates.
WeMos ESP32
I received two of these in May of 2017 at a price of $6.90.
Mine are not the Lolin modules, which have a lot more pins.
They are small boards with only 8 pins on each side, along with 2 extra and hard to get to pins.
Note that early esp32 silicon had bugs and issues. And some (many? all?) of the lolin boards ship with the early
faulty silicon, so beware and keep your eyes open.
Reverse Engineering
I am not doing any of this, yet anyway, despite putting a lot of energy into reverse engineering the ESP8266.
But other folks have picked up the baton: