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OTA bootloader service description

AN4486

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OTA bootloader service description

The OTA bootloader service is addressed through the files btl.[ch] provided within the

BlueNRG DK software which supports both BlueNRG and BlueNRG-MS devices.

The following provides a brief description of the OTA bootloader service and related

characteristics:



Bootloader OTA service: the bootloader service



aci_gatt_add_serv(UUID_TYPE_128, UUID, PRIMARY_SERVICE, 10,

&btlServHandle)



Btl Image characteristic: contains information related to the lower and higher bounds

of free memory as suggested by the current application that includes the OTA

bootloader service



aci_gatt_add_char(btlServHandle, UUID_TYPE_128, UUID, 8,

CHAR_PROP_READ, ATTR_PERMISSION_NONE,

GATT_INTIMATE_APPL_WHEN_READ_N_WAIT,16, 0, &btlImageCharHandle)



Btl new image characteristic: contains the base address and the size of the image that

the master wants to send over-the-air



aci_gatt_add_char(btlServHandle, UUID_TYPE_128, UUID, 9,

CHAR_PROP_READ|CHAR_PROP_WRITE|CHAR_PROP_WRITE_WITHOUT_

RESP, ATTR_PERMISSION_NONE,

GATT_INTIMATE_APPL_WHEN_READ_N_WAIT |

GATT_SERVER_ATTR_WRITE,16, 0, &btlNewImageCharHandle)



Btl new image content characteristic: contains a 16-byte block of firmware image data

sent by the master (through a characteristic write command) along with some control

information such as block sequence number (2 bytes) and checksum for integrity

check (1 byte)



aci_gatt_add_char(btlServHandle, UUID_TYPE_128, UUID, 20,

CHAR_PROP_READ|CHAR_PROP_WRITE|CHAR_PROP_WRITE_WITHOUT_

RESP, ATTR_PERMISSION_NONE,

GATT_INTIMATE_APPL_WHEN_READ_N_WAIT |

GATT_SERVER_ATTR_WRITE,16, 0, &btlNewImageTUContentCharHandle)



Btl expected image sequence number characteristic, through which the slave device

notifies the master about the next block it expects



aci_gatt_add_char(btlServHandle, UUID_TYPE_128, UUID, 4,

CHAR_PROP_NOTIFY|CHAR_PROP_READ, ATTR_PERMISSION_NONE,

GATT_INTIMATE_APPL_WHEN_READ_N_WAIT, 16, 0,

&btlExpectedImageTUSeqNumberCharHandle)

Note: OTA bootloader service and proprietary 128-bit UUID characteristics are defined

within the file btl.c.

2.1

Bootloading transactions

This section walks through the steps for OTA bootloading:

Once the master and slave running the OTA bootloader service are set, a discovery

procedure needs to be done in order for the two devices to connect. Discovery is

achieved by listening to advertisements coming from devices within the radio range

(active scan) and selecting the ones containing the OTA BTL service UUID 128-bits

within the scan response.

The name of the selected device will be read from the advertising message to be

utilized by the master in order to enhance the slave identification procedure.

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