The vast majority of CableWorld devices are based on the Gigabit Ethernet Controller II module, the so-called GEC II. The module is capable of performing various tasks such as control the device, measure and modify transport streams. The microcontroller on the module also provides the web interface. When the design of the board began, we chose a microcontroller called Luminary, developed by Texas company. The Texas company has now forced us to make changes because they stopped manufacturing the Luminary microcontroller. The microcontroller is becoming increasingly difficult to obtain while its price is constantly rising. We had to find a new controller to replace the old one, which was not an easy task because few microcontrollers have an Ethernet input (MAC + PHY).
In the end, we choose a Texas model again, partly because we have a development and programming environment for it, and most of our experience so far has been good with the Texas company’s product. The new controller type is TM4C1294NCPDT, which is built into a 128-pin TQFP package. Anyone who hasn’t worked with such controllers yet has a hard time imagining that the replacement required more than 1 year of development work. Considering that the documentation for the 128-pin IC is more than 2,000 pages, and the wiring of the pins has to be dealt with individually when making the PCB, one year of work is no longer so incredible. The printing of the PCB has already been completed last year and we assembled the first five samples, so we are past the most difficult part of the replacement. We are currently writing the new software and testing the panel that we are calling GEC III.
In recent years, while using the old GEC II module, a number of modification needs have arisen. We are now developing these demands into the new GEC III module. One of these was the increase in the size of SDRAM, which doubled in the new version, so 3 pieces of 512 Mbit RAM were placed on the GEC III module.
The circuits on the GEC II and GEC III panels operate on a 3.3 V voltage, which has so far been produced directly with a 3.3 V power supply. Because of the sensibility of the circuits, a small voltage drop at the connector can cause instability in the board. The optimal solution is when the power supply provides a higher output voltage (for example 12 V) so we put a high-efficiency switching power supply on the board which receives 12 V and provides a stable 3.3 V to the circuits.
Also, a new possibility is that Raspberry Pi 4 and GEC III panels can be connected inside the device. An I2C bus, multiple serial and parallel buses were added to the panel as well. In addition, a display port has been included, which we will present later in related applications.
Since Raspberry Pi 4 does not have its own clock module (time data can get from a time server), we have also placed a clock/calendar module with a battery on the board.