ESP32 Testing and Development

Job review listings on LinkedIn ask for a lot; you must have 10 years experience with X product, you must have generated at least Y Million in company revenue in the last year, etc etc. I wanted to expand my skillset and to do so I wanted to delve into the world of Microcontroller design. while I’ve used many different microcontroller families and models, I’ve never had to really diagnose issues with one, and thus my skills surrounding them could be called into question by more senior engineers. Therefore I’ve come up with the plan to expand my understanding of this field by developing my own range of custom boards using various ESP32 SoC modules.

the plan is to start simple with boards that merely utilise the already existing components built into the Wroom line up of ESP32 SoCs, but as I continue and learn more about the topic to eventually transition to more niche models for specific tasks. the eventual goal is to have the ability to rapidly design and prototype a board for a custom task and to do so cheaply and quickly.

Step 1: What ESP32 to use?

There are many types of ESP32 all designed for different tasks, but consulting the website and multiple documents just increased the barrier to entry, by overloading me with pages and chrome tabs each with a single piece of relevant information. I found that the Wikipedia page on the ESP32 does a good job of summarising key details into concise lists, if more general information is needed then I recommend the table below, which is an updated copy of Fabian Oriccardi’s markdown document on current ESP32 models.

	ESP8266	ESP32	ESP32-S2	ESP32-S3	ESP32-C3	ESP32-C6	ESP32-C2 / ESP8684
Announcement Date	2014, August	2016, September	2019, September	2020, December	2020, November	2021, April	2022, April
Main processor	Tensilica L106 32-bit (up to 160MHz)	Tensilica Xtensa 32-bit LX6 (up to 240MHz) (optionally dual core)	Tensilica Xtensa 32-bit LX7 (up to 240MHz)	Tensilica Xtensa 32-bit LX7 dual core (up to 240MHz)	RISC-V 32-bit (up to 160MHz)	RISC-V 32-bit (up to 160MHz)	RISC-V 32-bit (120MHz)
SRAM	160KB	520KB	320KB	512KB	400KB	400KB	272KB
ROM	0	448KB	128KB	384KB	384KB	384KB	576KB
JTAG	X	✓	✓	?	✓	✓	✓
Cache	32 KB instruction	64KB	8/16KB (configurable)	?	16KB	32KB	16KB
WiFi	Wi-Fi 4 (only up to 72.2Mbps)	Wi-Fi 4	Wi-Fi 4	Wi-Fi 4	Wi-Fi 4	Wi-Fi 6	Wi-Fi 6
Bluetooth	X	BLE 4.2 (upgrade to 5.0, with limitations)	X	BLE 5.0	BLE 5.0	BLE 5.0	BLE 5.0
Ethernet	X	✓	X	?	X	X	X
RTC memory	768B	16KB	16KB	16KB	8KB	?	?
PMU	✓	✓	✓	?	✓	✓	✓
ULP coprocessor	X	✓	ULP-RISC-V	?	X	X	X
Cryptographic Accelerator	X	SHA, RSA, AES, RNG	SHA, RSA, AES, RNG, HMAC, Digital Signature	SHA, RSA, AES, RNG, HMAC, Digital Signature	SHA, RSA, AES, RNG, HMAC, Digital Signature	SHA, RSA, AES, RNG, HMAC, Digital Signature	SHA, AES, RNG
Secure boot	X	✓	✓	✓	✓	✓	✓
Flash encryption	X	✓	XTS-AES-128/256	✓	XTS-AES-128	XTS-AES-128	✓
SPI	2	4	4	?	3	3	3
I2C	1	2	2	?	1	1 + 1 low power	1
I2S	1	2	1	?	1	1	0
UART	2 (one TX only)	3	2	?	2	2 + 1 low power	2
SDIO Host	0	1	0	2	0	0	0
SDIO Slave	0	1	0	0	0	0	0
GPIO	17	34	43	44	22	22	14
LED PWM	5	16	8	?	6	6	6
MCPWM	0	6	0	2	0	0	0
Pulse counter	0	8	4	?	0	X	X
GDMA*	0	0	0	?	6	X	1
USB	X	X	USB OTG 1.1	?	Serial/JTAG	X	X
TWAI**	0	1	1	?	1	2	X
ADC	1x 10-bit SAR	2x 12-bit SAR, up to 18 channels	2x 13-bit SAR, up to 20 channels	?	2x 12-bit SAR, up to 6 channels	1x 12bit SAR, up to 7 channels	1x 12bit SAR, up to 5 channels
DAC	X	2x 8-bit	2x 8-bit	?	X	X	X
RMT	1x transmission + 1x reception	8x transmission/reception	4x transmission/reception	?	2x transmission + 2x reception	1x transmission + 1x reception	X
Timer	2x 23-bit***	4x 64-bit	4x 64-bit	?	2x 54-bit + 1x 52-bit	1x 52-bit + 2x 54-bit	1x 52-bit + 1x 54-bit
Temperature Sensor	✓	✓	✓	?	✓	✓	✓
Hall Sensor	X	✓	X	?	X	X	X
Touch Sensor	0	10	14	?	X	X	X

For my first Microcontroller board, I decided to use the ESP32-2C otherwise known as the ESP8684, as it seems to be the simplest modern microcontroller from ESP replacing the ESP8266. it has many benefits over the ESP8266 including increased SRAM and ROM as well as the ability to diagnose issues mid code execution using the JTAG interface. Another positive change is the addition of blue-tooth and wifi6, allowing for easy connectivity with other devices and the network.

Step 2: Picking additional required parts:

To program and run the microcontroller SoC however, more components are needed, specifically a USB to serial module is needed to flash the microcontroller with code and a voltage regulator for managing power and regulating it to the 3.3V required of the ESP8684. I could also add some other ICs that increase the functionality of the board and add specific features, but because this is my first attempt. I want the overall board to be simple.