IMXRT1062: Boot issues when muxing GPIO_SD_B1_05

[Carlio]

Hi there,

I´m using the example “hello_world_virtual_com” provided by the SDK for the IMX1062 as a base for an application we are developing on a custom board. On our board there is no SWD/JTAG so in order to debug (and later use Freemaster) we are in need of the usb to vcom functionality. To flash the board we are using the NXP Boot Utility and in the boot device configuration we use the Winbound_W25QxxxJV default template since we have a winbound QuadSPI flash on our board.

First the example works without an issue, however, we need to be able to mux the GPIO_SD_B1_05 pin in order to communicate with a hall sensor that is connected to this pin. But when configuring the GPIO_SD_B1_05  pin in the pinmux tool and initializing it in main(), the virtual com example stops working. It is not only the vcom functionality but just toggling a LED will not work.

I found out that the  GPIO_SD_B1_05  is used  for the flash DQS and it is probably that, when configuring pin GPIO_SD_B1_05, we get some problems with the boot but I don’t really understand why this issue occurs.

Is there a way to go around this issue, like disable the DQS on GPIO_SD_B1_05 and muxing it to another pin that supports this functionality? If so, can this be done in the MCU Boot Utility? Or is it possible to disable the DQS all along and use a slower frequency? 

Tips on ideas on how to proceed are warmly welcomed. 

Best regards,

Carl

[Carlio]

Thank you @nickwallis ! That did the trick! (Note, If someone uses the MCUXpresso IDE the settings for configuring .readSampleClkSrc to use kFlexSPIReadSampleClk_LoopbackInternally and .serialClkFreq to kFlexSpiSerialClk_60MHz that can be found in project->xip->evkmimxrt1060_flexspi_nor_config.c .) 

[nickwallis · Accepted solution]

See this thread for an explanation:

https://community.nxp.com/t5/i-MX-RT/target-crashes-writing-to-register-SW-MUX-CTL-PAD-GPIO-SD-B1-05...

-Nick