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Honored Contributor I

Are the possibilities to use pins as custom I/O's for external wiring - NEEK



I've got a NEEK-Starter-Board (Cyclone III, Multimedia Board, Terasic LCD Daughter Card) to work with. The overall goal is to wait for button touches on the touchscreen, then send appropriate commands over a communication bus to an external controller. Afterwards I would like to print the controllers reply to the LCD. 


I just finished my work on my GUI and I now would like to connect the NEEK to an external communication bus. For that I need to connect 2 or 3 wires to the FPGA, depending on the kind of bus (don't know jet whether SPI or CAN). As the FPGA board and the Multimedia board are connected via a HSMC connector directly there are no IOs accessible. Do you have an idea how to get direct IO access to the FPGA without the use of adaptercards for the HSMC connector? 


Now, I try to find a way to use one of the multimedia connectors (Audio, VGA, ...). The problem is that most of these signals are modified by the MAXII 2210 chip. Spending some more time on that I figured out that there are some Pins which might be suitable: 

- VGA_VS - The vertical sync of the VGA is not modified by the MAXII 2210 

- VGA_HS - Same thing here 

- Also the Data and Clock pin of the PS/2 and some of the SD-Card reader might be possible. 

The problem here is: Between these ports and the FPGA there is a voltage translator. So I don't know whether that might work out or not. 


Is anybody of you experienced in this topic? 


Any information and hints are appreciated. Thanks! 




It is possible to program the MAXII 2210 chip after removing two jumpers. Do you know of a "design example", "source code" or anything else for that chip?
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Honored Contributor I

Well it's true that the LCD mezzanine card pretty much consumes any and all available IO. It does seem to me however that there is an I2C bus that is accessible for use.  

If you look at your NEEK main board near the HSMC connector you'll see 4 through-holes for an unstuffed header. The pins have the labels "SDA,SCL,3V3, and GND5". I would look into finding out if there is someway you can make use of those.  


Also, you do have the RS-232, Ethernet, and PS2 ports that you could use for communication.  


Honored Contributor I



In the meantime, I tried to find as many pins as possible. Here are my results: 

- SDA, SCL possible 

- UART_TXD possible, with an advantage: you can see the traffic via the TXD-status LED 

- UART_RXD not possible, it's just one-way, so not usable as an output 

- SD-Card possibe 

- VGA_VS, VGA_HS couldn't get these working, no idea why ... 


Unfortunately, there are pull-up resistors and resistors in series within the PS2 and SD-Card lines which might bring disturbances. Could cause problems with some busses. 


not tested yet: 

- PS2 clk and data pins 



I don't know yet which pins to use as all of them have further electronical components connected. Maybe I have to find a way to use the first unused third (~30 pins) of the HSMC. Are there any HSMC adapters which split up the three parts?