Nexys 2/Spartan 3E LED blinker and counter

Here's a verilog project I coded for the Nexys 2/Spartan 3E - a simple LED counter and multiplexed 7 segment display counter.

Download project

FT232H

FT232H - High speed USB 2.0 interface. Can communicate via high speed parallel FIFO interface at up to 40MBytes/s. Should be very easy to interface to an FPGA or MCU.

pSRAM memory test for the Nexys 2

This is a very simple pSRAM memory test for the Nexys 2 with the Spartan 3E 500 FPGA. Simply writes and reads back the memory.

Note that the RAM chip on the Nexys 2 board is the MT45W8MW16BGX in a BGA package.

module Main(
	input wire clk,
	output wire [7:0] Led,
	input wire [3:0] btn,
	output wire MemOE,
	output wire MemWR,
	output wire RamAdv,
	output wire RamCS,
	output wire RamClk,
	output wire RamLB,
	output wire RamUB,
	output wire [23:1] MemAdr,
	inout wire [15:0] MemDB
	
);

//Registers
reg [31:0] state = 0;
reg [7:0] rLed;

reg rMemOE = 1;
reg rMemWR = 1;
reg [15:0] rMemDB;
reg [23:1] rMemAdr;


//Static assignments
assign RamCS = 0;	//chip select is always low (enabled)
assign RamClk = 0;	//clk is disabled in asynchronous mode
assign RamAdv = 0;	//address valid can always be pulled low in asynchronous mode
assign RamLB = 0;	//lower byte is enabled
assign RamUB = 0;	//upper byte is enabled

//Register assignments
assign MemOE = rMemOE;
assign MemWR = rMemWR;
assign MemDB[15:0] = rMemDB[15:0];
assign MemAdr[23:1] = rMemAdr[23:1];

assign Led[7:0] = rLed[7:0];

always @(posedge clk)
begin
	if(btn[0]) 					//btn[0] is reset/write
		state <= 0;
	else if(btn[1])				//btn[1] is read
		state <= 50;
	else if(btn[2])				//btn[2] just toggles Led[7]
		rLed[7] <= ~rLed[7];	
	else begin
		case(state)
			0: begin
				rMemAdr <= 23'b0;		//set address to 0
				rMemDB <= 16'h0505;		//write 0x0505 to the data bus
				rMemWR <= 0;			//pull write enable low to write the data
				state <= 10;
				end
			10: begin
				rMemWR <= 1;			//pull write enable to high again
				end
	
			50: begin
				rMemDB <= 16'bzzzzzzzzzzzzzzzz;		//set the data bus to high impedance
				rMemOE <= 0;						//pull output enable low to start a read
				state <= 60;
				end
			60: begin
				rLed[3:0] <= MemDB[7:0];			//set the LEDs to show the data
				state <= 70;
				end
			70: begin
				rMemOE <= 1;						//pull output enable high again
				end
		endcase
	end
end


endmodule

UBW32 Generic USB demo

I ported and cleaned up the generic USB demo from the Microchip application libraries. The project is designed to work with the UBW32.

Requirements:

• UBW32 or any other pic32 microcontroller board.
• PICKIT/ICD/REALICE to program your board, or a linker script to load with the USB bootloader.

Download

Download the project and compile/flash the firmware onto your chip. Open the USB/Device - LibUSB - Generic Driver Demo host program for your operating system. Attach your device to the host and connect.

PIC32 Timer1 example code

The following code snippet opens and uses Timer1 as an interrupt. In your initialization sequence:

//Open Timer1 with 1:8 prescaler (80MHz -> 10MHz), with period of 10, therefore tick = 1MHz.
OpenTimer1(T1_ON | T1_PS_1_8 | T1_SOURCE_INT, 10);
ConfigIntTimer1(T1_INT_ON | T1_INT_PRIOR_2);
INTEnableSystemMultiVectoredInt();

And the interrupt handler:

void __ISR(_TIMER_1_VECTOR, ipl2) _Timer1Handler(void) {
	mT1ClearIntFlag();
	//Your code
}

PIC32 pin change interrupt

The following is a quick snippet for interrupt on change pin

void __ISR(_CHANGE_NOTICE_VECTOR, ipl2) ChangeNotice_Handler(void) {            
	mPORTDRead(); //Need to read the port (see PIC32 datasheet)
	mCNClearIntFlag();
	//Your code...
}

And, in your initializing code:

mCNOpen(CN_ON | CN_IDLE_CON, CN13_ENABLE | CN14_ENABLE | CN15_ENABLE, CN_PULLUP_DISABLE_ALL); //See plib documentation and PIC32 datasheet
ConfigIntCN(CHANGE_INT_ON | CHANGE_INT_PRI_2);
INTEnableSystemMultiVectoredInt();	 

Crimping a modular connector without a cimp tool

So it turns out that the guy at the local electronics store near the university is too damn cheap to lend me a crimp tool for literally 10 seconds, and would rather charge me $5 to merely crimp a header onto the end of a cable. So I decided to crimp the modular header (for ICD) onto a the cable myself. I decided to instead use a flat ribbon cable (like the computer IDE cable) since they're thinner and much more flexible than the 6 wire telephone cable I bought. The wire-to-wire pitch is slightly larger than for a normal telephone type (6p6c) cable so you can't insert it directly, but if you pull the individual wires apart to about 5mm from the end, and then put them in, it works out well. Crimping without a tool was a snap - took only about a minute with nothing more than a flat head screwdriver to push in the tab as well as each of the contacts.