I wouldn't use the Cypress USB Serial Test program for the final implementation but you could write a program using WinUSB for the last two steps.
Here is the setup of the breakoff part of the PSoC4100 prototype board with a CY7C65211-24LTXI single channel interface (CY7C65215 has dual channels, but not in this prototype board) Also I didn't want to break-off the one in the PSoC4200, but the USB-Serial part is the same for both $4 prototype boards.
I have an RTC board that uses an NXP PCF8563 that uses I2C at 400KHz
I already have all the software and drivers installed so I'm not going to go through that.
So first I open the Cypress USB-Serial Configuration Utility after plugin in the board to my PC USB port, and selected my USB-Serial (Single Channel) target and clicked on Connect:
I left the USB configuration alone, but you can change the VID/PID manufacturer and product strings etc, also left the IO levels to CMOS (you can select TTL) and clicked on the SCB tab:
Next I selected the mode to be I2C and clicked Configure
Edit: Note that you can set the notification LEDs to use GPIO pins to drive transmit and receive individual LEDs or a single one for both tx/rx
Selected 400KHz and set it to be in Master mode and ok.
Back to the previous screen click on program.
And it will come back with success (if everything is setup right).
Now, since I can't be bothered to write a WinUSB sample program, I just used the provided USB Serial Test Utility from Cypress, but you really wan't to write your own and talk to your VID/PID or search for your custom manufacturer and/or product string when enumerating USB devices.
But this test utility will allow me to just read the RTC, Also I didn't bother to program this RTC so it's as it came from China because I never had time to play with it until now, but just wanted to see if I could read data from it using this USB-Serial chip.
So I started the test utility and changed the Vendor ID and Product ID to what I programmed the chip with.
Then clicked the Read & verify data, and of course the verify part didn't work but it displays what the RTC is sending at 400KHz
The bus pirate might have easier tools, but for the price ($4 plus you get to keep an Cortex M0 ARM processor) it's a good alternative, you can't even buy the chip and make your own board for the fraction of that break off board that comes with that prototyping board.
Edit: You can also program the CapSense for capacitance touch, and unsused GPIOs mode on top of the Battery Charge Detect for battery powered devices.