ARM software

This section describes our platform’s ARM software. This software runs on Linux on the PS side of the chip and is responsible for the interaction with X-HEEP implemented on the PL side of the chip.

Software development kit (SDK)

We support the user with a dedicated Python class, called x_heep, that allows you to easily use all the platform’s functionalities.

Basic functions

__init__()

It initialises the class and loads the bitstream.

load_bitstream()

It loads the bitstream.

compile_app(app_name)

  • app_name is the name of the application to be compiled.

It compiles the application with the specified name.

run_app()

It runs the last application that has been compiled.

run_app_debug()

It runs the last application that has been compiled in debug mode so that you can debug it with GDB.

Warning

This function is not supported by Jupyter notebooks!

These last two functions are realised through a combination of OpenOCD, GDB and Screen. OpenOCD is used to implement the JTAG protocol driving the required GPIO pins, while GDB is used to send the needed commands to OpenOCD in order to program the X-HEEP main memory and run or debug the application. Finally, Screen is exploited to extract the stdout of the application running on X-HEEP.

../_images/arm_sw.svg

Virtual Flash functions

init_flash()

It allocates in the DDR memory a buffer of 32KB and stores its base address in the configuration register of the virtual Flash address adder. Then, initialises it to zero and returns the allocated virtual Flash buffer object.

reset_flash(flash)

  • flash is the name of the virtual Flash buffer object.

It initializes to zero the complete virtual Flash buffer.

write_flash(flash)

  • flash is the name of the virtual Flash buffer object.

It writes to the virtual Flash buffer the content of the file named flash_in.bin from the application folder.

Warning

The input binary file must be named flash_in.bin and located in the application folder. The file cannot have a size higher than 32KB (the size of the virtual Flash)!

read_flash(flash)

  • flash is the name of the virtual Flash buffer object.

It reads the virtual Flash buffer and stores the content in a file named flash_out.bin that will be created in the build folder.

Virtual ADC functions

init_adc_mem()

It maps the virtual ADC BRAM (8KB) and initialises it to zero. Then, returns the virtual ADC memory object.

reset_adc_mem(adc_mem)

  • adc_mem is the name of the virtual ADC memory object.

It initializes to zero the complete virtual ADC memory.

write_adc_mem(adc_mem)

  • adc_mem is the name of the virtual ADC memory object.

It writes to the virtual ADC memory the content of the file named adc_in.bin from the application folder.

Warning

The input binary file must be named adc_in.bin and located in the application folder. The file cannot have a size higher than 8KB (the size of the ADC BRAM)!

read_adc_mem(adc_mem)

  • adc_mem is the name of the virtual ADC memory object.

It reads the virtual ADC memory and stores the content in a file named adc_out.bin that will be created in the build folder.

Performance estimation functions

init_perf_cnt()

It maps the performance counters and resets them. Then, returns the performance counters object.

reset_perf_cnt(perf_cnt)

  • perf_cnt is the name of the performance counters object.

It resets the performance counters.

start_perf_cnt_automatic(perf_cnt)

  • perf_cnt is the name of the performance counters object.

It starts the performance counters in the automatic mode.

start_perf_cnt_manual(perf_cnt)

  • perf_cnt is the name of the performance counters object.

It starts the performance counters in the manual mode.

stop_perf_cnt(perf_cnt)

  • perf_cnt is the name of the performance counters object.

It stops the performance counters.

read_perf_cnt(perf_cnt)

  • perf_cnt is the name of the performance counters object.

It reads the performance counters and stores their values in a CSV file named perf_cnt.csv that will be created in the build folder.

estimate_performance()

It combines the values of the performance counters file with the frequency of the platform’s clock (20MHz) and calculates the performance of each IP in the architecture. Then, prints the performance to the stdout and stores the values in a CSV file named perf_estim.csv that will be created in the build folder.

Warning

This function can only be called after the read_perf_cnt() function!

Energy estimation functions

estimate_energy(cells)

  • cells is the type of cells, LVT or HVT, you would like to use for the energy estimation.

Our energy model combines the values of the performance file with the values of the power file and estimates the energy of each IP in the architecture. Then, prints the energies to the stdout and stores the values in a CSV file named energy_estim.csv that will be created in the build folder.

Warning

This function can only be called after the estimate_performance() function!

Note

Our team is working to allow the user to specify not only the type of cells but also the clock frequency (ranging from 10 MHz to 250 MHz, for LVT and from 10 MHz to 100 MHz, for HVT)!

Memory map

Base address

Length (Byte)

Description

0x40000000

0x2000

ADC memory

0x43C00000

0x0004

Flash AXI address adder

0x43C10000

0x0100

Performance counters