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Clearing out the previous program on a micro:bit

PROBLEM

How do I clear the memory on a micro:bit?

I want to start a new class with 30 empty micro:bits, how do I do that?

How do I ‘reset’ the micro:bit so that any existing programs are wiped out?

SOLUTION

There is a feature built into later versions of the USB interface chip software on the micro:bit, that can be used to quickly erase the flash on the device. This could be used to clear a large number of micro:bits ready for the next lesson. ┬áIt’s called automation mode.

1) Check what version of interface firmware is installed on your micro:bit

a) plug in the micro:bit and browse to the MICROBIT drive

b) open file DETAILS.TXT

c) look for the ‘interface version’ and note down the number.

2) If necessary, update interface firmware to at least 0241

If you have a version of interface firmware lower than 0241, you must update your interface firmware to allow the automation mode feature to be used. Follow the steps in the following article to do this, then come back here:

https://support.microbit.org/solution/articles/19000019131-how-to-upgrade-the-firmware-on-the-micro-bit

3) Once you have verified that you have at least interface firmware version 0241, the next step is to enable automation mode

a) Download the auto_on.cfg attachment from this article and store it on your computer hard disk somewhere

b) hold the RESET button on the back of the micro:bit firmly

c) at the same time as holding the RESET button, drag the auto_on.cfg file to the MICROBIT drive

d) this will enable a new feature. Now let go of RESET and power cycle your micro:bit

e) open DETAILS.TXT again and make sure that you see ‘Automation Allowed: 1’ in the file

4) Now download the erase.act file attached to this article and store it on your hard disk.

5) If ever you want to quickly erase the program memory on the micro:bit, just drag erase.act onto the MICROBIT drive and it will quickly erase the whole program memory.

WARNINGS

1) If the program memory of the micro:bit is completely empty, you will not be able to use the Bluetooth pairing mode at all. To recover the bluetooth pairing feature, please follow the instructions in this article:

https://support.microbit.org/solution/articles/19000026073-how-to-re-instate-bluetooth-after-previously-using-micropython

2) Compass calibration data will be lost as a part of erasing the flash memory. Next time you flash a new .hex to your micro:bit, if you are using the compass, you will have to recalibrate it as described in this article:

https://support.microbit.org/solution/articles/19000008874-what-does-it-mean-when-the-micro-bit-says-draw-a-circle-

TECHNICAL REFERENCE INFORMATION

[1] enabling automation mode in DAPLink:

https://github.com/mbedmicro/DAPLink/blob/master/docs/ENABLE_AUTOMATION.md

[2] Erasing program flash using an MSD command:

https://github.com/mbedmicro/DAPLink/blob/master/docs/MSD_COMMANDS.md#action-commands

ATTACHMENTS

auto_on.cfg

erase.cfg

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