ESP32 pin damaged? (low resistance to ground)

[doooku]

Hello!

I've been using ESP32 for quite some time, and so far I was impressed with its capabilities. At our company we've designed sensoric platform based on ESP-WROOM32 with web browser and remote data reading, and everything worked well for the first two prototypes. However, when first batch of sensors was produced, we've encountered some kind of bug, and we are not sure if it's flaw in our design or in the ESP32 module.

The problem manifests as several different failures:

• I2C communication failure
• Unability to program ESP32 (which previously worked)

After some investigation we suspect the cause of the problems is similar - some pin of the ESP-WROOM32 module has unusually low resistance to ground (around 20 ohms). Same pin on working sensor has resistance to ground in the order of tens of kiloohms. From this observation I suspect that the pin is somehow damaged (electrostatic discharge?).

Resistance is measured between ground and the pin. Device was not powered while measuring.

In the first case (I2C failure) either SDA or SCL is damaged, causing the bus line to be held low, thus preventing any communication on I2C. In the second case either RX or TX of UART0 is damaged, thus preventing communication with programmer. I am at loss as to what is the cause of this. I've double-checked hardware design guidelines and I've found no problems with our design. I have only two ideas:

• Pin damaged from ESD
• Poorly done EMC on my board, causing voltage spikes to be induced on traces (from radio tx, maybe?)

Occurrence of this problem seems random, yet it happens quite often. All of the boards were fully functional after assembly, but after few weeks, half of all boards had this problem.

Has anyone encountered similar problem? And how vulnerable are ESP32 pins to ESD in general?


Thank you for your time.

[markposg]

I teach a course where we had about 100+ students use the ESP32. After one semester we had probably 100 NodeMCU ESP32's die for unknown reasons. While many were blown from stupid things students do, this number is much higher than we had from previous years where we were using ESP8266's. I'm wondering if it could be ESD primarily because 1) the winter here had much lower humidity than the summer class (much higher static discharge incidents) 2) the students had to hit the "flash button" GPIO0 with this ESP32 which they didn't need to do for the ESP8266's so the opportunity for discharge was about 100's more common. Of course the students didn't have ESD mats, wrist straps or any of the precautionary tools professionals may use.

Does ESD seem like a reasonable cause for failure?

[narender64]

Even I am facing the similar issue. I am post grad in electronics h/w , have more than 20 years experience working with microcontrollers , I am very well aware of the misuse issues of port pins and related damages like ESD issues, over loading, over driving the inputs etc. I have taken such care in my designs with esp32 wroom module/ devkit modules/ M5 module etc, but in general I have observed many port pin failures without any attributable reasons ! I am observing random failures of port pins in the case of esp32 , it may show short with adjacent pins, gets its drive weakened. Is there any expert advice! what is to be taken special care in the case of esp32 designs ?