Reading a PS/2 mouse

Seems like there is problem initializing the mouse. The host pulls the clk down to start initializing; however, the mouse clock doesn't start after the host releases the clk.

Just a few quick questions -

• What FPGA? It is 5V compatible?
• Are you driving the line to 'Z' (tri-state), or to a '1'?

The fact that the line is about 4V smells bad - could you have contention?

Jeremy

Thanks for your reply, Jeremy!

I was using Xilinx Spartan 2E 200 on Digilent D2Sb with DIO4 extension board. I'm driving the line to 'Z' not to '1'. However, after probing the PS/2 port (6 pin mini-DIN)on the board without attaching a mouse, I found that the data and clk stay at '0' always (according to the schematic from Digilent, there is no pull up circuit on both PS/2 data and clk lines). When I probe the corresponding fpga pins, they work as I programmed (logic 1 = 3.3V, logic 0 ~0V). Seems like the fpga couldn't take control of the port!

I will try to use another board (XESS XSA3S1000 with Xstend V3.0) and see if this happens.

A stupid question but... If you are using a daughterboard and are onl reading 0V, are you sure that

- The daughterboard is correctly connecte

- You use the proper IO pins on FPG

Yes I did, those are the only IO pins that I can use and it is correctly connected.

np.

!? Sounds a touch odd. If the pins are connected to the PS/2 port, then you would expect the port and the pins to be the same. If you take the PS/2 port as the reference, then it would perhaps be a case of enabling the pullup resistors in the IOB (xc_pullup attribute for synplify - the xilinx attribute is PULLUP (from memory))). This wouldn't explain your original problem though.

Guess you need to find out why the pins and the port don't match :) The other point of course, is that you state that the protocol uses 5V - but you're driving 3.3V?

Jeremy