add note about manually triggering bootloader

README.md

@@ -20,3 +20,5 @@ All SAM parts have a slightly broken boot ROM which presents a serial interface
 Due to the brokenness inherent in the bootloader, the recommended tool for updating the firmware is [the Python script in this repository] which treats the USB device implementing the CDC-ACM USB device class as a raw vendor device and directly interacts without using the serial interface and triggering bugs. This is advantageous due to finer grained control over packet boundaries - if SAM-BA receives commands split across subsequent USB packets, an error condition will arise. Unfortunately, Windows does not offer the ability for userspace programs to detatch kernel drivers, so the device must be interacted with as a serial device.
 
 [BOSSA](www.shumatech.com/web/products/bossa) is a third-party open-source cross-platform tool which implements the required serial protocol and works around the afforementioned bugs. Install the latest version from [SourceForge](http://sourceforge.net/projects/b-o-s-s-a/files/) and follow the instructions [in the documentation](http://www.shumatech.com/web/products/bossa) to flash the m1000.bin file included in this repository.
+
+Before you use BOSSA, you must first manually trigger the bootloader on the ADALM1000. This can be done by shorting out the small jumper on the "top" of the board, by the labels for the PIO connector. The device should disconnect from USB and re-enumerate as a SAMBA bootloader device / USB modem.