New to NIOS

[Altera_Forum]

Hello all, 

 I am a moderately experienced fpga programmer but brand new to NIOS.  So, I have used SOPC to generate a NIOS II and designated onchip memory to go with it. From Eclipse I have been able to run the HelloWorld program (by linking to the .sopc file) and run the program onto the fpga.   Now, I want to know how to write code in main() to access the onchip memory in my NIOS II in the fpga.   Ultimately I want to write a register I define in my fpga so I can control things in my hardware from C code i write in eclipse.  I don't know where to start.

[Altera_Forum]

See chapter 9 of 

Nios II Software Developer's Handbook iowr_32direct

[Altera_Forum]

Please allow me to give you a bit more detail because I've been there and still not sure how to proceed. 

 I'm using the Nios II/e along with jtag uart, sysid and onchip memory.  My objective here is to write to the onchip memory a value that I can access and pinout to an LED on my cyclone III fpga.  So 2 issues as I see it: 1) how do I actually write to the onchip memory from my nios II (i.e what is the syntax of a write and do i need some external libs)  2) once i write to the onchip memory, how do i actually access that memory from outside of my sopc project. How do I interface with the rest of my fpga?? Currently my nios system only has a reset and a clock port. How in the world am I to access the contents of memory of the onchip memory and then connect that to a pin on my fpga?  nios_test_system_1   (  .clk_0 (clk40),  .reset_n (1)  );

[Altera_Forum]

For that particular action, you're going to want to instantiate an output PIO, 1 bit wide (assuming 1 LED), and hook it up to your LED at the top level. 

 In your Nios II code, you'd just use a PIO macro to write a 1 or 0 to control the LED. Look at the count_binary example for a decent sample of how to do this.  Cheers,  --slacker

[Altera_Forum]

thank you. that was exactly what i needed. i have my LED's blinking happily :)