C++ API Usage Examples

Load a Bitstream

To write a bitstream file to the /lib/firmware directory, you can use the Device class to write the file directly.

Device dev;
dev.write_to_file("/lib/firmware/design.bit", bitstream_data);

To load a bitstream onto the FPGA, you can use the Device class to set the bitstream attributes and download it. Ensure that first the bitstream exists in /lib/firmware.

Device dev;
dev.set_bitstream_attrs("design.bit", false);
dev.download("design.bit");

Allocate and Use contiguous memory buffer

To allocate a contiguous memory buffer that can be used for device operations, you can use the BufferRemote class. First, you must have an instance of XrtBufferManager, initialised with an xrt device obtained from the XRT C++ API. Then, you can create a BufferRemote object with the desired size and type by passing in the relevant XrtBufferManager.

This buffer can be used to read/write data directly.

xrt::device device = xrt::device(0);
XrtBufferManager mgr(device);
BufferRemote buf(1024, "<float", mgr, true);  // 1024 bytes, float type, cacheable

float* arr = reinterpret_cast<float*>(buf.virtual_address());
arr[0] = 3.1415f;
buf.flush();

MMIO Access

To perform memory-mapped I/O operations, you can use the MMIO class. Each instance of MMIO represents a memory-mapped region, allowing you to read and write values at specific offsets.

MMIO mmio(0xA0000000, 0x1000);  // Base physical address, size 4KB
mmio.write(0x0, 0x1);           // Write value 1 at offset 0
uint32_t val = mmio.read(0x0);  // Read from offset 0