⚠️ NOTE: If this is your first time using F1, you should read How To Create an Amazon FPGA Image (AFI) From One of The CL Examples: Step-by-Step Guide first!!
This hello_world example builds a Custom Logic (CL) that will enable the instance to "peek" and "poke" registers in the Custom Logic (CL). This example demonstrate a basic use-case of the Virtual LED and Virtual DIP switches.
The cl_hello_world example demonstrates basic Shell-to-CL connectivity, memory-mapped register instantiations and the use of the Virtual LED and DIP switches. The cl_hello_world example implements two registers in the FPGA AppPF BAR0 memory space connected to the OCL AXI-L interface. The two registers are:
- Hello World Register (offset 0x500)
- Virtual LED Register (offset 0x504)
The Hello World Register is a 32-bit read/write register. However, in order to demonstrate that the register is being accessed correctly, the read data returned for the register will be byte swapped.
The Virtual LED register is a 16-bit read-only register that shadows the lower 16 bits of the Hello World Register such that it will hold the same value as bits 15:0 of the Hello World Register.
The cl_hello_world design utilizes the Virtual LED and DIP switch interface which consists of two signals described in the cl_ports.vh file:
input[15:0] sh_cl_status_vdip, //Virtual DIP switches. Controlled through FPGA management PF and tools.
output logic[15:0] cl_sh_status_vled, //Virtual LEDs, monitored through FPGA management PF and tools
In this example the Virtual LED Register is used to drive the Virtual LED signal, cl_sh_status_vled. In addition, the Virtual DIP switch, sh_cl_status_vdip, is used to gate the Virtual LED Register value sent to the Virtual LEDs. So, for example, if the sh_cl_status_vdip is set to 16'h00FF, then only the lower 8 bits of the Virtual LED Register will be signaled on the Virtual LED signal cl_sh_status_vled.
While running on F1, the developer can use the FPGA tools fpga-get-virtual-led to read the LED values on the CL-to-Shell interface.
While fpga-set-virtual-dip-switch tool is used to set the DIP switch values on the Shell-to-CL interface.
The Hello World example does not use most of AWS Shell interface, hence the unused signals are tied off.
At the end of cl_hello_world.sv file, there is a specific include command for an interface-specific .inc file, to handle the tie-off's for every unused interface.
The following table displays information about the CL that is required to register it as an AFI with AWS. Alternatively, you can directly use a pre-generated AFI for this CL.
| Key | Value |
|---|---|
| Shell Version | 0x04261818 |
| PCI Device ID | 0xF000 |
| PCI Vendor ID | 0x1D0F (Amazon) |
| PCI Subsystem ID | 0x1D51 |
| PCI Subsystem Vendor ID | 0xFEDD |
| Pre-generated AFI ID | afi-03d11a4ea66e883ef |
| Pre-generated AGFI ID | agfi-0fcf87119b8e97bf3 |