The host uses this command to trigger the device to immediately show a pre-loaded image on the display, provided the device is not in a mode that has exclusive use of the display (such as during a transaction). This is an immediate and temporary directive. For a solution that affects the device’s idle page behavior on a more permanent basis, see Property 1.2.3.1.1.1 Custom Idle Page Image. This command is different from Show Bitmap Image - Command 0x1823 in that the bitmaps are pre-loaded and persistently stored in the device and can not be composited with each other.
The sequence of events is as follows:
1
Prepare the image slot
The host makes sure it has loaded the image into at least one of the device’s Custom Idle Page Image slots using Start Send File to Device (Unsecured) - Command 0xD812.
2
The host makes sure the device is in Active/Idle state (meaning the display is fully powered on and is not in a mode that has exclusive use of the display, such as processing a transaction).
3
The host calls this command to show the image loaded into the desired slot number.
4
The device shows the specified image on the display until the device is no longer in Active/Idle.
Tag
Len
Value / Description
Typ
Req
Default
Tag
Len
Value / Description
Typ
Req
Default
If the request started successfully, the Request Status in the message wrapper is All Good, Requested Operation Was Successful.
1821 = Show Image (Display Only) - Command 0x1821
81
01
Custom Idle Page Image Number
0x01 = Show custom image 1
0x02 = Show custom image 2
0x03 = Show custom image 3
B
R
82
01
Display Option
0x00 = Default to cover/uncover the top status bar depends on the current status of the display. If the current display shows the top status bar, the Show Image command won’t cover the top status bar. If the current display doesn’t show the top status bar, the Show Image command will cover the top status bar.
0x01 = Cover the top status bar regardless of the current status of the display.
0x02 = Not cover the top status bar regardless of the current status of the display.
B
O
0
83
01
Display Time
0x00 = Show image until device changes state
B
O
0
End of any wrappers, at minimum including Request Message
1821 = Show Image (Display Only) - Command 0x1821
No parameters.
End of any wrappers, at minimum including Response Message
Beginning of any wrappers, at minimum including Request Message
Beginning of any wrappers, at minimum including Response Message