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DISPLAYS & interfaces The firmware has two constituent parts: Image_Transfer_Master.ino – This is firmware that has been loaded onto the first module, which is referred to as the ‘Master’. Image_Transfer_Slave.ino – This is firmware that has been loaded onto second module, referred to as the ‘Slave’. The images are stored on an SD card attached to the Master module, and are loaded one at a time into processor RAM before being transferred to the FT800 EVE device on this module for inflation and eventual storage inside the IC’s internal graphics RAM. The image filenames are hard coded and stored in the ImageName array. This means that the user can easily Fig. 3: A pair of HMI sub-systems connected to one another via an RS232 interface. change the images simply by supplying new files and filenames. The loadJpegImage() function firstly checks that the file relating to the image to be loaded actually exists, then issues a CMD_LOADIMAGE command to the FT800 to load a JPEG image and inflate it. Once this is done it initiates the loadJpegBytes() function, which transfers the file data from SD card to FT800, supplying the data required by the CMD_LOADIMAGE command, in order that the FT800 can inflate the JPEG data and store it in the graphics RAM. The loadJpegBytes() function loads and transfers the JPEG file to the FT800. This is done 512byte blocks at a time, until the entire file has been processed. Communication between Master and Slave When the two VM800P modules are connected together in the way described in Figure 3 the Master establishes communications with the Slave, to which the Slave sends a response. A command signal COMMAND_ IMAGE_START is sent in order to initiate the image transfer process (this command includes information on the size of the image). To this the Slave returns a signal to confirm it is ready for image transfer. For every line of the image a COMMAND_ IMAGE_SLICE signal is sent from the Master to the Slave (which contains the line number of the image being sent, together with the image data which has been read from the FT800’s graphics RAM). A COMMAND_IMAGE_SLICE_CONFIRMED signal is returned, indicating that the Slave has received the image data, subsequently transferred it to the FT800 and is now ready to accept the next command. A COMMAND_IMAGE_DONE signal is sent to indicate that the image transfer has been completed. In conclusion, the simplified HMI design strategy that is made possible by treating both image and audio content as objects has many notable upshots. In addition to lowering procurement costs, saving board space and shortening development times, it also makes it far easier to connect multiple HMIs together so that they can pass useful data between one another. This means that HMI units no longer need to be thought of in isolation, there is the option for them to become part of a much bigger system. Custom-made touch display for outdoor and demanding applications TBy Pierre Leveugle he use of TFT LCD displays become popularized by electronic products and systems for outdoor applications such as vending machines, parking meters, charging stations and other products designed by industrialists for use by private individuals. In order to be differentiated and raise the interest of users, the manufacturers are innovating to offer equipment that combine external design, technological performance (high-end applications), quality graphic display and user-friendly interface (especially for touch commands). It is with that in mind that Clairitec has been requested to participate in the development of a tailor-made touch command interface according to the specifications given by the manufacturer. The HMI controls a charging station for electric vehicles. It is a product designed for drivers and set up in strategic and mainly outdoor locations. This interface is integrated in a new product and therefore must combine innovation and sturdiness. With that in mind, there were several constraints that needed to be taken into account: - Display 7’’ with high brightness and 90° viewing angle - Backlight: 800 cd/m² minimum - Resolution: WVGA minimum - Anti-reflective glass - Protection against vandalism to meet the protection standard IK10 Pierre Leveugle is Marketing & Communication Manager at Clairitec – www.clairitec.com – He can be reached at p.leveugle@clairitec.com 32 Electronic Engineering Times Europe June 2015 www.electronics-eetimes.com


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