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Say cheese

Microcontrollers with I2C interfaces are at the heart of Hasselblad’s most advanced camera system yet. By Jim Bryant and Lasse Sageryd.

Hasselblad's new H1 is something of a milestone for the Swedish based manufacturers of arguably the best camera in the world. The centrepiece of the company's first new medium format system in 45 years, it is a new 645 format camera system, using either digital backs or film magazines. In addition, the H1's operating system and interface allow feature, controls and settings to be customised to suit specific work methods or situations.

Essentially, the H1 comprises a number of mix and match modules: grip and body (the so called 'house'), lens, viewfinder and cassette style film magazine. The key to its modularity, versatility and ease of use is of course the electronics embodied in the system. Microcontrollers in each of these modules communicate via a bus, effectively turning the camera into a distributed processing system.

At first, designers looked at the feasibility of using CANbus, but rejected the idea because it would involve the high overhead of a CAN controller. Instead, a simpler I2C (two wire) bus in a multimaster implementation enables a variety of microcontrollers to coexist without conflict – and communicate seamlessly. Also, Hasselblad has previous experience of using I2C for the controllers in 200 and 500 series cameras.

The main controller is located in the grip. A 16bit microcontroller was chosen for this role which also drives the entire camera interface. This man/machine interface provides, for example, interfacing with the liquid crystal display. This microcontroller is also responsible for all the sequencing and synchronisation (for example during the exposure) in the camera system. Three Fujitsu 8bit microcontrollers (MB89530 series) are used for the lens, viewfinder and film magazine respectively. Another low power controller is located in the magazine as the lcd needs to be active when the magazine is detached from the body.

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Graham Pitcher

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