ESP32-PICO-Mini

[julien2711]

Hello,

Me and a friend of mine are working on a LED-Juggling ball. We are just now in the prototype phase trying to get our own HW operational. As an electrical engineer with quite some experience in HW design, I'm responsible for designed of the internal PCB (LDO, Bat ctrl, USB/UART bridge, ESP32-PICO-MINI, IMU).
I was giving the system assembly my second shot today (frist failed). I got most things running (LDO, Bat ctrl, USB/UART bridge). Then I tried to flash the ESP32-PICO-Mini. To my surprise I got an error with the flash. As far as I understand the datasheet, there is no way to interfere with the flash since it doesn't have external pins.

Here the log of the programmer:

Code: Select all

Sketch uses 235005 bytes (17%) of program storage space. Maximum is 1310720 bytes.
Global variables use 16376 bytes (4%) of dynamic memory, leaving 311304 bytes for local variables. Maximum is 327680 bytes.
esptool.py v3.3
Serial port COM8
Connecting......
Chip is ESP32-PICO-V3-02 (revision 3)
Features: WiFi, BT, Dual Core, 240MHz, Embedded Flash, Embedded PSRAM, VRef calibration in efuse, Coding Scheme None
Crystal is 40MHz
MAC: 30:83:98:d5:0e:54
Uploading stub...
Running stub...
Stub running...
Changing baud rate to 921600
Changed.
WARNING: Failed to communicate with the flash chip, read/write operations will fail. Try checking the chip connections or removing any other hardware connected to IOs.
Configuring flash size...
Flash will be erased from 0x00001000 to 0x00005fff...
Flash will be erased from 0x00008000 to 0x00008fff...
Flash will be erased from 0x0000e000 to 0x0000ffff...
Flash will be erased from 0x00010000 to 0x00049fff...
Compressed 17120 bytes to 11841...

A fatal error occurred: Packet content transfer stopped (received 8 bytes)
A fatal error occurred: Packet content transfer stopped (received 8 bytes)

I'm using the most recent Arduino IDE (1.8.19) with your software package (2.0.3) for it. I verified with a devkit that on the computer side everything is fine. Program I was using was the example "GetChipID"

If anybody of you have ever seen this before let me know. So far I don't think this could be caused by an external connection. I suspect it could be damaged by soldering with water ingress but I would like to hear a second opinion.
In the first try I suppose I destroyed some of the components thermally and/or due to water ingress (going up to 300 deg C). To make the second attempt a success I stored all components in a desiccator in vacuum for 2 weeks and used low temperature solder paste with only 225 deg C reflow soldering station. The ESP32 I used had, before I put them in low vacuum, been exposed to normal atmosphere for 1 week.

Unfortunately I didn't have equipment to bake the components before use.

I attached a screenshot of the existing connections. The SPI Flash is DNF so all the SPI pins are not connected.

Thanks and kind regards,
Julien Schreier

[ESP_Sprite]

From the datasheet:
"The module integrates a 3.3 V SPI flash, so the pin MTDI [GPIO12] cannot be set to 1 when the module is powered up."

[julien2711]

Thanks a lot. I missed that.
I copied the schematic from the dev-kit. But missed that that this Res wasn't fitted.

[julien2711]

Hi again,

thanks another time for helping me out with my stupidity. I was soldering all day on Sunday. I removed the resistor yesterday and everything works fine now.

So if anyone wants to know: Vacuum of better than ~ -100kPA (still low vacuum) for two week is enough for a MSL3 device to undo a little more than 1 week (just at the border) of 25degC @ 60% humidity exposure. I used my works lab desiccator with occasional nitrogen flushing (for opening). I didn't bake the device before soldering.

kind regards