System Overview; System Architecture Description; Figure 5. System Architecture - ST STM32 User Manual

UM0908
2

System overview

2.1

System architecture description

The architecture of the system is shown in
camera using ZigBee communication. The system has two units; one is the "camera unit"
while the other is the "monitoring unit". Both units are based on the STM32 microcontroller.
Figure 5.
In the camera unit, the STM32 microcontroller is interfaced to the camera through GPIOs.
Through these GPIOs, the microcontroller takes data from the industry standard ITU 8-bit
interface of the camera. On powering up, the camera module is initialized through an I
interface for the streaming of jpeg images. During this Initialization appropriate registers in
the camera module are updated to get images as per requirements. In this unit, the camera
module is programmed for streaming jpeg images rather than bmp format, as this helps in
reducing the image transfer time on the ZigBee network.
Furthermore, this unit fully utilizes the advantages of the STM32 built-in DMA controller to
capture images from the camera module, therefore keeping the microcontroller free for other
purposes. The DMA controller is triggered through the STM32 timer which receives interrupt
on the rising edge of the PCLK signal. The DMA unit transfers the whole image in the
microcontroller's RAM from where it is sent onto the ZigBee network by the microcontroller
through the SPI based ZigBee module. During the time the image is transferred onto the
ZigBee network the DMA stays in STOP mode. Once the whole image is transferred onto
the ZigBee network the DMA captures another frame from the camera and the process is
repeated. In a case where there is no monitoring unit present in the system the camera unit
discards the present frame and captures the new frame.
In this system, the ZigBee network is established using the SN260 module which works on
channel 20. The camera unit acts as a coordinator and the monitoring unit acts as a node.
This camera unit is also capable of storing images in the uSD card available on the unit. The
images are stored using the FAT file system and therefore they can be easily viewed on a
PC using a card reader. The system can be triggered to capture images through a trigger
switch, or an external PIR sensor can be interfaced for this purpose. This unit is capable of
working both on USB power supplies and battery.
www.BDTIC.com/ST
System architecture
Doc ID 17087 Rev 1
Figure 5 below. The system works as a wireless
System overview
2
C
7/33