Unresolved issues with rk3399 UART and PBP adapter voltage
I hate to be that guy, annoyingly reminding about inconvenient to hear things, but still, I need to, since this silence and lack of reaction is a bit frustrating.

As we know, it turned out, rk3399's UART2 (or all of them) is put by Rockchip in the non-standard 3.0V power domain. This affects RockPro, PBP and future HardRock. Literally every USB-UART adapter is 3.3/5V but not this 3.0V and even though the difference can seem insignificant, still, rk3399's datasheet claims maximum of 3.15V for the domain, so it is rather questionable if it is safe to use.
Farther, to make things worse, it turned out, that the UART to earphone jack adapter for PBP being sold on the official Pine64 store, has inside the controller with IO lines set to 5V! without switching capabilities. This difference is already enough to make at least it cause instabilities when used.
This brings up two questions:
1) Is it possible to provide (for the newer revisions of RockPro and upcoming HardRock boards) onboard mechanisms, that will overcome troubles created by Rockchip and make using 3.3V adapters connected to 3.0V SoC lines safe? and if it is, is it planned?
2) why is the dangerous, incompatible UART-earphone jack adapter still being sold without even warning of its incompatibility? and are there plans to fix it?

sorry, I understand, that this may cause inconveniences, but the above issues are certainly inconvenient themselves. I am more than surprised about this silence on both sides. it's so often needed to use that UART, still there are such problems with this, doesn't it require attention or I missed something?
ANT - my hobby OS for x86 and ARM.

Messages In This Thread
Unresolved issues with rk3399 UART and PBP adapter voltage - by z4v4l - 02-19-2020, 04:04 PM

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