Configure alternative GPIO functions at boot time on VF61

My application needs all five UARTS. How do I configure the GPIO pins to use the alternative functions at boot time? I would like not having to build a custom boot loader just for this.

  1. The Vybrid GPIO tool does not allow saving to “boot time”, only to RAM
  2. The serial debug prompt allows for setting the GPIO config block, but there is no member for the MUX_MODE field.

To load the UART driver, the pins must be configured at boot time, correct?

I added the two extra registry keys UARTD and UARTE under HKLM\Drivers\BuiltIn, but loading them failed (obviously) since the GPIO pins haven’t been configured.

I looked at the GPIO library functions, to maybe set it up from application code. But they don’t seem to modify boot time settings.

Thank You.

Ebbe Nilsson

To load extra serial ports check this article:, I believe you might have already gone through the mentioned article, but you did not save the added registry keys and values for that use SaveReg(Start > Programs > ColibriTools > SaveReg) and then reset your module, after that UART driver will be initiated at boot itself.

After saving the registry changes changing registry settings from UART would not be required from your application.

Also please note that you have to disable SD card driver to use all UARTs.

Thank you Rajat. No, I had missed that article. I did save my reg entries, but failed to add the TX and RX pin info on the two non-standard UARTs. So, the driver performs the IO pin configuration, that makes perfect sense.