Hi folks,
I have several ESP32-POE-ISO units and am working on a data logging application.
The system is powered by a 12V, nominal, LiFePo4 battery with the option to solar charge.The ESP32-POE-ISO has a LiPO connected and can charge its self when required.
I note from the documentation that USB and 5V power should not be applied at the same time. This makes development and particularly debugging a bit of a pain it also means that I MUST disconnect the USB after an upload before the EXT power is connected, again a bit of a pain.
If I use a USB Isolator, Like this (https://www.amazon.co.uk/WMLBK-Isolator-USB-Isolation-USB-Industrial-Isolators/dp/B098LHMHPK/ref=sr_1_11?crid=3NF849JJRCV20&dib=eyJ2IjoiMSJ9.96TEKM1YRQLbtHJyuTjVPVnieaYVOcl34F-z2zKqK1KmA7cNGVSPEabvn2Xw7xfO3TLyXoyY8qq11ObORBi63ojViZHHG785to12w5w6w2KbhAR-nOaGjT_nJ0kiekYPoMkGkV_Hns2duwFWqtFrPoKrMeNrtwqLIk4ejF0ztysD5sFWq6C3MasXxiUVSeq7heG5p8d4gv7ntzEfpd8zZj7aAw5VtVDWK44ow_KYVTo4U4H_RVZBWhrmiTPg-Drj6hHqWieQlPz7qmTSu-pVFtTS1L_8J9VHHrlFHew3EKI.e36aIntuDnAPcGihRxaLzySUmV-b_EOiDotFu8O_uQc&dib_tag=se&keywords=usb+isolator&qid=1705616258&refinements=p_85%3A20930949031&rnid=20930948031&rps=1&s=electronics&sprefix=usb+isolator%2Celectronics%2C127&sr=1-11), can I still read serial dfata when the EXT power is on?
Your understanding of the board and the issue and the way you operate the board are correct. Disconnect external power, apply USB, debug (program, etc), disconnect USB, re-apply external power.
USB isolator should fix the issue. Hardware-wise the product you linked should be alright (ADuM3160 is well-known isolator chip). We have own USB-ISO with ADuM4160 (ADuM4160 is certified for 5kV and voltage range is a bit wider, while ADuM3160 for half of that - 2.5kV and narrower voltage range):
https://www.olimex.com/Products/USB-Modules/USB-ISO/
Notice that USB isolators like that only support low and full speed USB (no high speed or better), so there can be driver issues or USB speed limit.
Thanks, that is good to know...
Help much appreciated.