At Adafruit, we really like the UF2 bootloader for installing software like CircuitPython on microcontrollers. UF2 allows you to drag-and-drop UF2 files and has a nice LED/NeoPixel indicator. No special DFU/firmware-updater software is required and you can use any computer to program a UF2-bootloader device. Once installed, you can access the UF2 bootloader by clicking the reset button twice in a row.

But what do you do with a fresh chip, or if the UF2 bootloader on your device has become corrupted? This guide will walk you through the steps of installing the UF2 bootloader using the ROM bootloader built into all RT10xx chips using software called sdphost or sdphost.exe on your PC, Mac, or Raspberry Pi.

Now it's time to configure your board to enable the ROM bootloader, which is sometimes called the "serial downloader".  The RT series chips will start the USB ROM bootloader when certain 'strapping pins' are set on hardware boot.

On the MIMXRT1010-EVK board

• Move jumper J1 to position 3-4 so that the board can be powered from USB port J9
• Ensure jumper J27 is at position 2-3 so that reset switch SW9 resets the microcontroller. Use switch SW9 when the text below tells you to press reset.
• Use connector J9 for your USB connections. Don't use connector J41, it's a debug connector.

For Metro M7 RT1011

Find SE Blank RT Family

Once you've set the jumpers for your board, plug in the board with a USB cable. You cannot just press reset, do a full hardware reboot

Your computer should see a new USB device called SE Blank RT Family. Note, it is not a mountable USB device or COM port, and will not appear in the file browser.

In windows, we found it under Control Panel > Hardware and Sound > Devices and Printers

If not, check the switch positions & cables.

There are two ways to install sdphost: Adafruit builds executables for Windows, Linux, and Mac as a part of the tinyuf2 project, and NXP offers a version on pypi.

Getting "sdphost" from pypi

If your computer has python & pip installed, this is the preferred method.

NXP offers the "NXP Secure Privisioning SDK" (SPSDK) on PyPI.

You may wish to create a virtual environment for this task, or use pipx to install the command using an isolated environment.

$ pip install spsdk
# many lines of output snipped
Successfully installed spsdk-1.11.0

$ pip install spsdk
# many lines of output snipped
Successfully installed spsdk-1.11.0

Getting "sdphost" from the tinyuf2 project

If your computer doesn't have Python & PIP available, you can use this method.

Getting the TinyUF2 bootloader file

Open up a terminal window and issue two commands with sdphost, changing the name of the .bin file as appropriate:

sdphost -u 0x1fc9,0x0145 -- write-file 0x20206400 tinyuf2-imxrt1010_evk.bin
sdphost -u 0x1fc9,0x0145 -- jump-address 0x20207000

sdphost -u 0x1fc9,0x0145 -- write-file 0x20206400 tinyuf2-imxrt1010_evk.bin
sdphost -u 0x1fc9,0x0145 -- jump-address 0x20207000

The hex numbers above are the same for any RT1010/RT1011 board. Different processors need different parameters. These are the values used by tinyuf2 for various evk boards:

# sdphost command for imxrt1010_evk:
sdphost -u 0x1fc9,0x0145 -- write-file 0x20206400 tinyuf2-imxrt1010_evk.bin
sdphost -u 0x1fc9,0x0145 -- jump-address 0x20207000

# sdphost command for imxrt1020_evk:
sdphost -u 0x1fc9,0x0130 -- write-file 0x1000 tinyuf2-imxrt1020_evk.bin
sdphost -u 0x1fc9,0x0130 -- jump-address 0x2000

# sdphost command for imxrt1024_evk:
sdphost -u 0x1fc9,0x0130 -- write-file 0x1000 tinyuf2-imxrt1024_evk.bin
sdphost -u 0x1fc9,0x0130 -- jump-address 0x2000

# sdphost command for imxrt1060_evk:
sdphost -u 0x1fc9,0x0135 -- write-file 0x1000 tinyuf2-imxrt1060_evk.bin
sdphost -u 0x1fc9,0x0135 -- jump-address 0x2000

# sdphost command for imxrt1064_evk:
sdphost -u 0x1fc9,0x0135 -- write-file 0x1000 inyuf2-imxrt1064_evk.bin
sdphost -u 0x1fc9,0x0135 -- jump-address 0x2000

# sdphost command for imxrt1010_evk:
sdphost -u 0x1fc9,0x0145 -- write-file 0x20206400 tinyuf2-imxrt1010_evk.bin
sdphost -u 0x1fc9,0x0145 -- jump-address 0x20207000

# sdphost command for imxrt1020_evk:
sdphost -u 0x1fc9,0x0130 -- write-file 0x1000 tinyuf2-imxrt1020_evk.bin
sdphost -u 0x1fc9,0x0130 -- jump-address 0x2000

# sdphost command for imxrt1024_evk:
sdphost -u 0x1fc9,0x0130 -- write-file 0x1000 tinyuf2-imxrt1024_evk.bin
sdphost -u 0x1fc9,0x0130 -- jump-address 0x2000

# sdphost command for imxrt1060_evk:
sdphost -u 0x1fc9,0x0135 -- write-file 0x1000 tinyuf2-imxrt1060_evk.bin
sdphost -u 0x1fc9,0x0135 -- jump-address 0x2000

# sdphost command for imxrt1064_evk:
sdphost -u 0x1fc9,0x0135 -- write-file 0x1000 inyuf2-imxrt1064_evk.bin
sdphost -u 0x1fc9,0x0135 -- jump-address 0x2000

These commands run really quickly, in well under a second. Once the sdphost commands finish, your board will re-connect via USB, for instance as RT1010BOOT. However, before you do anything else, you need to return the switches to their usual position.

 Then re-plug your device or use its reset button. This mode is sometimes called "FlexSPI boot".

Once again your device will connect as a BOOT device with a disk drive appearing. If it doesn't, double check the DIP switch settings and try pressing RESET twice in quick succession to activate the UF2 bootloader. If you've previously loaded software such as CircuitPython via UF2, it was not erased when you installed TinyUF2 and it will automatically be booted.

You can now drag any compatible UF2 file such as CircuitPython onto the drive.

To access the UF2 bootloader again at any time, press the reset button twice in quick succession. You can upgrade CircuitPython or TinyUF2 itself using the UF2 bootloader. Only if TinyUF2 becomes corrupted will you need to follow the instructions with sdphost again.

Continue installing CircuitPython by following the steps in this guide.