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How flashing works in K32L2B in production board

Question asked by Eric Smith on Jul 10, 2020
Latest reply on Jul 13, 2020 by Eric Smith

Hey, I'm trying to figure out the requirements for the production board so we can flash from the factory as well as in production. We are using the same MCU as in the FRDM-K32L2B3 dev kit. Could somebody read this and let me know if I'm on the right track as a sanity check? Thanks so much!


1. The MCU comes from the factory with the kinetics ROM bootloader preinstalled. By default all the peripherals are enabled and it will boot to ROM. We will be able to communicate to the bootloader via the USB0_DP/DM pins using the blhost utility and flash our user program. Is all that correct?


2. We'd like to have a way to boot to ROM on our production board (such as a jumper). For this to be possible, we need to use blhost to set FOPT[BOOTPIN_OPT] to 0 when we initially flash. Then we just have to assert the BOOTCFG0 pin to boot into ROM. This raises two last questions: a) What does asserted mean and what the wiring for that looks like? b) do we need a reset button when we assert BOOTCFG0 or will it do it automatically jump to ROM or can we assert on power up?