After reading a lot of posts it seems like I am on the right track for doing this correctly, but yet it still does not quite work.
Kernel: http://www.wiki.xilinx.com/Zynq+2015.4+Release
I took the zedboard release file, extracted it, and then copied it over to an SD card and booted from that. Seems to work fine.
Tools: Vivado 2015.4 and SDK 2015.4
After that, I create a hardware .bit file using an AXI GPIO IP block to connect to the PS to the switches. I generate the .bit file, export it to the SDK, and then launch the SDK.
Based on the system.hdf file, the axi_gpio_0 is located at 0x41200000. So this is where I assume I need to mmap /dev/mem in order to access the values.
I start a new application project, select Linux, and create the C++ project. Then I program the FPGA after the OS has been loaded from the SD card.
The code I use to try and access the values at the AXI_GPIO address is below. I try to map just one byte because the GPIO register with the values is in the first byte (at least I believe it is...). I have also tried mapping 0xFFFF bytes (which is the end address of the AXI GPIO block) and getpagesize() bytes as well (so 4096 in this case).
Even more aggravating is when I do a bare metal application and de-reference 0x41200000, it accurately reads the switches.
I also tried it as a Linux C application, but that too hangs so it is not C++ versus C related as far as I can tell.
I am using the SDK's TCF to download and run the application. It runs in /tmp/ (not sure if that is important or not...)
#include <iostream>
#include <unistd.h>
#include <sys/mman.h>
#include <sys/fcntl.h>
const unsigned int64_t gpioAddr = 0x41200000;
int devMemSwitchTest()
{
tint x = 0;
tint fd = 0; fd = open("/dev/mem", O_RDWR | O_SYNC);
tvolatile unsigned int* addr = NULL;
tvolatile unsigned int* start = NULL;
toff_t offset = gpioAddr & ~(getpagesize()-1);
tif (fd == -1)
t{
ttperror("Failed to open /dev/mem: ");
ttclose(fd);
ttreturn -1;
t}
tstart = (unsigned int*)mmap(NULL, 1, PROT_READ | PROT_WRITE, MAP_SHARED,
tttfd, offset);
tif (start == MAP_FAILED)
t{
ttperror("ERROR with mmap: ");
ttmunmap((void*)(start), getpagesize());
ttclose(fd);
ttreturn -1;
t}
taddr = (unsigned int*)start + (gpioAddr - offset); //this happens to evaluate to addr = start since it is already page aligned.
t
t//unsigned int y = *((unsigned int*)start); <-- freezes here if not commented out!!
tmunmap((void*)(start), getpagesize());
tclose(fd);
treturn 1;
}
int main() {
tstd::cout << "Attempting to opend /dev/mem" << std::endl;
tdevMemSwitchTest();
tstd::cout << "We made it!!!" << std::endl;
treturn 1;
}
Thanks in advance for any help provided! This has been driving me crazy for the past two days now...
Mark
