| ## 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. |
| ```shell |
| $ ./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 |
| ``` |
