View source for FPGA registers access from Linux userspace on OPOS93 SP

[[Category:FPGA]]
[[Category: OPOS93_SP]]


== Introduction ==

The ''flexio_armabus'' kernel driver is mapping the FPGA address space in a file ''/dev/armabus''. For further informations, see [[OPOS93_SP Interfaces description]].

== Setting address ==

Address should be set using the ''lseek()'' C function on the ''/dev/armabus'' file.

<source lang="c">
int fd = open("/dev/armabus", O_RDWR);
lseek(fd, 8, SEEK_SET); // Set address to 0x0008
</source>

== Read/write ==

Access to the bus should be done using ''read()'' and ''write()'' functions.
Write or read size should be multiple of 4.

<source lang="c">
write(fd, buf, 8); // Write 2 words of 32b
</source>

<source lang="c">
read(fd, buf, 4); // Read 1 word of 32b
</source>