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SoCSIM

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SoC Simulator is a simple SoC (System-on-chip) + Board emulator intended to practice programming in FreeRTOS for a MCU.

It uses freertos-addons to allow using FreeRTOS on a Linux box. Edit Makefile to point variables to installation directory. It uses imgui to build a GUI to show input/output and devices virtually connected to the MCU. Current set-up uses SDL and OpenGL implementation.

SoCSIM GUI

The emulator includes a HAL (HAL.h) to interface with the emulated Hardware.

The Hardware is emulated in the following files:

  • Memory emulates a memory map.
  • SoC emulates behaviour of MCU + Board.

License

This project is licensed by GPLv3. See LICENSE file for more details.

Installation

It is required a C/C++ compiler compatible with C++17. Tested with gcc 10.2.0 on ubuntu.

git clone https://github.com/FreeRTOS/FreeRTOS-Kernel.git
git clone https://github.com/michaelbecker/freertos-addons.git
git clone https://github.com/mariusmm/SoCSIM.git
cd SoCSIM

SDL2 is required, install it with:

sudo apt install libsdl2-dev libsdl2-2.0-0

Build

Build is based on cmake, so in SoCSIM directory run the following commands:

mkdir build
cd build
cmake ..
make
./SoCSIM

Build documentation

cd build
make doc

The documentation is generated in doc/ directory in html and latex format. In case you want to generate pdf from latex, you need to run make in the doc/latex/ directory

Virtual peripherals

GPIO

There are 4 GPIO ports (PORTA, PORTB, PORTC & PORTD).

  • Button 1 is connected to PORTA, pin #0
  • Button 2 is connected to PORTB, pin #1
  • LED 1 is connected to PORTC, pin #7
  • LED 2 is connected to PORTD, pin #12

Interrupt Controller

There is a basic Interrupt Controller with only two registers, NVIC_CTRL and NVIC_IRQ.

PWM TIMER

This timer is only able to generate a PWM signal, it counts from 0 to value ADDR_TIMER_TOP and starts over. When timer value is less than ADDR_TIMER_CMP output is '0', when greater output is '1'.

Timer input clock runs at 16 MHz and can be pre-scaled by a value from 1 to 256 (powers of 2 only).

RTC

A very basic RTC timer, with 1 second precision that store seconds in the RTC_CNT register (32 bits). It also has a compare register (RTC_CMP) to trigger an IRQ if both registers are equal.

TRACE

An ITM-like peripheral with a single register that prints out the characters written to its data register.

DAC

DAC peripheral able to generate a signal between 0 and 1 volts. The DAC works a 10 samples/second in continuous mode.

  • DAC_CTRL bit0 enables (1) /disables (0) DAC peripheral.
  • DAC_TRL bit7 enables (1) / disables (0) DAC IRQ. DAC triggers a IRQ when conversion is complete.
  • DAC_DATA bit 11-0 Data register (12 bits)

Watchdog

Watchdog peripheral that can halt de simulation (simulating a system reset). It includes a prescaler. The watchdog has a clock of 128 kHz and the counter starts with 2048. When counter reaches 0 resets the system (halts de simulation). There is a prescaler (WDOG_CTRL bits 15 to 8) to the input clock (powers of 2). Once enabled (WDOG_CTRL bit 0 to '1') watchdog can't be disabled.

To properly feed the Watchdog, the magic number 0x00505345 must be written to register WDOG_CMD.

Memory map

All registers are 32 bit width.

Address Register Comment
0x1000 GPIO A CTRL 1 - out , 0 - in
0x1004 GPIO A INT 1 - Interrupt enable, 0 - Disabled
0x1008 GPIO A OUT '1' or '0' set to output pin
0x100C GPIO A IN '1' or '0' set by the input pin
0x2000 GPIO B CTRL idem
0x2004 GPIO B INT idem
0x2008 GPIO B OUT idem
0x200C GPIO B IN idem
0x3000 GPIO C CTRL idem
0x3004 GPIO C INT idem
0x3008 GPIO C OUT idem
0x300C GPIO C IN idem
0x4000 GPIO D CTRL idem
0x4004 GPIO D INT idem
0x4008 GPIO D OUT idem
0x400C GPIO D IN idem
0xA000 INTERRUPT CTRL TBD
0xA004 INTERRUPT IRQ TBD
0xC000 ADDR TIMER CTRL Prescaler (15:8),
0xC000 ADDR TIMER TOP Top value
0xC000 ADDR TIMER CNT Timer counter value
0xC000 ADDR TIMER CMP Compare value
0xD000 ADDR RTC CTRL RTC control register
0xD004 ADDR RTC CNT RTC epoch time
0xD008 ADDR RTC CMP RTC compare register
0xF000 ADDR TRACE ITM like tracer
0x10000 ADDR DAC CTRL DAC control register
0x10004 ADDR DAC DATA DAC sample register
0x80000 ADDR_WDOG_CTRL Watchdog Ctrl register
0x80004 ADDR_WDOG_CMD Watchdog command register