Overview

Hello_world is the demo program used to show case basic functionality of the system. The test itself does 2 main things:

• Echo pin changes over UART.
• Echo SPI input over UART.

GPIO Changes Over UART

This function primarily exercises the GPIO and UART blocks. The test monitors changing values on the GPIO line and reports them over UART.

SPI Echo Over UART

All data input over SPI is echo'd on UART in a word aligned fashion. The sample output below is hello_world run on a verilator model.

$ ./Vtop_earlgrey_verilator --rominit=sw/device/boot_rom/rom.vmem --flashinit=sw/device/examples/hello_world/sw.vmem

Output:

dddd 1234 tgbf

SPI: dddd
SPI: 1234
SPI: tgbf