Designing a PCB

One of the things I wanna learn this month is to build hardware circuit on a pcb with commercial CAD software which are used to build circuits. The coolest thing about PCB software is that you can actually simulate a circuit without making the real hardware circuit. and it helps you analyze faults before you produce your circuit. I had designed a small PCB for SPI interface of an MMC/ SD card to a microcontroller. It was easy to design as there was no special circuitry needed for except for a few optional pull up resisters which should be used if the BUS is in open drain mode. If it is in push pull mode then there is no need of using pull up resistors. It all depends on which microcontroller we are using. If we are using a low end microcontroller like a PIC which is cheap we must use a Pull up on the data lines of the SPI bus. On the other hand if we use a High end microcontroller, it may provide options so that we dont need pull-ups. Overall PCB design a must learn thingy if you are into hardware and serious about becoming a hardware engineer.