Power-Cycling Watchdog to ensure i.MX RT based products don't hang in the ROM LOADER

[mjbcswitzerland]

Hi All

A weakness of the i.MX RT parts is that they can hang in the ROM LOADER and require power cycling - this can be due to a number of reasons but two that have often caused issues are due to the FlexRAM configuration and the QSPI flash:

- the use of certain FlexRAM configurations by user programs can leave the ROM LOADER in an inoperative state (the ROM LOADER tends to require 64k of OCRAM to be available, for example)
- if there is a software or watchdog reset during a QSPI flash programming or erase operation the QSPI flash will temporarily be in a state where its content cannot be read and so the ROM LOADER will stay in the ISP mode and never start the user program

Systems or products requiring high reliability (or basic quality) require a method of detecting and recovering from this state which can't be achieved by the i.MX RT itself.

In addition, people often search for a solution to ensuring the correct power sequencing on designs, plus how to efficiently be able to control ISP mode entry (search this forum for such discussions) without needing DIP switches as are typical on EVKs and fiddly on real product boards.

These typical requirements, coupled with the need for product reliability, were the impetus for the development of a very low cost and very low power Power-Cycling Watchdog as a standard solution for all i.MX RT base designs. This is now available in the uTasker project allowing the use of either a KL02Z8VFG4 or KL03Z8VFG4 (3mm x 3mm x 0.65mm in size and consuming uA of current) - whereby a KL08Z8VFG4 can be purchased for under 40 $ cents in quantity - as detailed in this document https://www.utasker.com/docs/iMX/uTasker_iMX_WDOG.pdf

Together with a simple push button it allows reset control, power sequencing, ISP mode selection and a high-reliability power cycling watchdog function to solve all i.MX RT product requirements in less space than typical passive circuits and even with free pins for adding special functions if ever needed.

Complete KL02 and KL03 builds are available in the uTasker project for those wanting to program the chips themselves (or potentially further customise to particular HW).

Pre-programmed devices are being considered in order to offer an general integrated solution as iMX RT standard support part and so feedback as to interest and demand would be useful.

Regards

Mark
[uTasker project developer for Kinetis and i.MX RT]
Contact me by personal message or on the uTasker web site to discuss professional training, solutions to problems or rapid product development requirements

For professionals searching for faster, problem-free Kinetis and i.MX RT 10xx developments the uTasker project holds the key: https://www.utasker.com/iMX/RT1064.html

[jeremyzhou]

It's interesting.

BR,

Jeremy