- Created on Monday, 08 August 2011 05:39
- Last Updated on Saturday, 21 January 2012 16:02
The aim of this project, as the title suggests, is to create a daughter card to interface to the development board found in Altera's Cyclone III Starter Kit.
The daughter card is being designed to provide USB communication between a PC and the starter kit board. Also, its purpose is to provide a rapid prototyping platform in the form of an attached solderless breadboard. One of the design goals of the project is to manage the cost of the board through judicious component selection.
This article documents the design of the daughter card from the card's requirements through to its PCB layout.
Daughter Card Requirements
To start the development process one of the first things we should do is gather a list of daughter card requirements. For instance, we already know that the daughter card is required to attach to the development board found in the Cyclone III starter kit. Hence, the daughter card and the development board should be interfaced using the High Speed Mezzanine Connector (HSMC).
A summary of the requirements can be seen in figure 1 below where each numbered item could be considered to be a requirement. For example, the item numbered, 1, refers to the HSMC requirement stated in the previous paragraph.
Figure 1: A block diagram of the solderless breadboard daughter card .
One set of requirements of the daughter card is the provision of a selectable voltage, 2 x 20 way IDC header connected to the HSMC interface. To allow either 3.3V or 5V connections, between the IDC header and the HSMC interface, bi-directional level shifters should be used to translate between 2.5V and 3.3V or 2.5V and 5.0V voltage levels. This set of requirements is depicted by items 2, 3 and 4 in figure 1 above.
The two sets of items labelled 5,7,9 and 6,8,10, in figure 1, provide two sets of level shifted connections between two 10-way female headers, respectively, and a solderless breadboard. The voltage levels of the headers should be adjustable to accept either 3.3v or 5.0v connections from the solderless breadboard.
Another set of requirements of the daughter board is the provision of a Serial Peripheral Interface (SPI) flash device multiplexed between the HSMC interface and and a Universal Serial Bus (USB) device, the Vinculum. The second interface of the Vinculum should be connected directly to the HSMC interface. These requirements are provided by the items labelled 12, 13 and 14 in figure 1.
Voltage regulators should provide a drop in voltage from 12V to 5.0V and 2.5V. Also, as mentioned before, the daughter card should host a PCB solderless breadboard. Items 11 and 16 respectively, in figure 1 above, satisfy this set of requirements. Finally, a 36 MHz crystal oscillator, item15, should also be connected to the HSMC interface.
So how much is it all going to cost? Well, to find out we could select components that satisfy the requirements above and approximate the cost.
To be continued