User guide

Atmel AVR2054: Serial Bootloader User Guide [APPLICATION NOTE]
8390D−WIRELESS−03/2015
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#define DFU_SUPPORT 1
3.6.2.2 Not-responding application or absent DFU
The application loaded to the flash by embedded bootloader may not include a DFU component as well as any special
code to deal with PC tool’s requests. In other cases when the DFU component is installed, it may stop responding due to
application failure. In these cases the device will not be able to process commands from the PC tool and thus initiate
reset and perform the firmware upgrade.
To load an image using bootloader into such device, connect JTAG’s PB7 pin to ground and reset the device. On an
Atmel SAM3S USB stick, these are the first two pins of the JTAG port and so can be connected with a jumper wire.
3.6.2.3 Additional remarks
Below are some more features:
• If one loads a firmware image to a device via the embedded bootloader for SAM3S and then reads the image
using JTAG it will not equal the initial binary image. The difference will be in the first four bytes where the
bootloader replaced the reset vector.
• Both the embedded bootloader and an application cannot be loaded via JTAG. If the device is first programmed
with the embedded bootloader and then with the application, by default the execution will start with the
application code. And if the application is programmed first, the embedded bootloader once programmed will
not be aware of the presence of the application.
3.7 BitCloud OTAU bootloader features
The BitCloud OTAU bootloader is a version of embedded bootloader that shall be used by BitCloud applications [3], [4]
that require firmware Over-the-Air upgrade (OTAU) feature. Unlike the common bootloader, the OTAU bootloader
contains a driver, which is able to transfer an image from an external flash device to the MCU’s flash memory as
illustrated in Figure 3-3.
Figure 3-3. OTAU embedded bootloader architecture.
The OTAU bootloader can also be configured to program an application image received via a serial interface to the flash
as a common serial embedded bootloader. But it has more functions required for OTAU support, such as driver to an
external flash device, image decryption, etc.
Atmel BitCloud PC Tool (described in Chapter 4) has a BitCloud OTAU tab that can be used to OTAU programming of a
remote node.
For further details on the topic of OTAU in BitCloud ZigBee PRO refer to [4] and [8].