TMS320F2800157-Q1: get zero while convert a negative float value to int

Part Number: TMS320F2800157-Q1

Tool/software:

Hi, experts,

Customer feedbacks that he try to explicitly convert a float variable to integer, if the value of float is negative, the value of the converted integer is 0. But according to his understanding of data type in C programming language, it should be parsed as a negative signed integer(if convert to a signed integer) or a big unsigned integer(if convert to a unsigned integer).

I did a simple test and get similar result. Please help to clarify the expected behavior while converting negative float to integer on C2000 devices. If there is some related documentation can guide customer, that will be perfect.

Thanks.

Below is my test code, and screenshot of values of each variable.

//#############################################################################
//
// FILE:   empty_driverlib_main.c
//
//! \addtogroup driver_example_list
//! <h1>Empty Project Example</h1> 
//!
//! This example is an empty project setup for Driverlib development.
//!
//
//#############################################################################
//
//
// $Copyright:
// Copyright (C) 2024 Texas Instruments Incorporated - http://www.ti.com/
//
// Redistribution and use in source and binary forms, with or without 
// modification, are permitted provided that the following conditions 
// are met:
// 
//   Redistributions of source code must retain the above copyright 
//   notice, this list of conditions and the following disclaimer.
// 
//   Redistributions in binary form must reproduce the above copyright
//   notice, this list of conditions and the following disclaimer in the 
//   documentation and/or other materials provided with the   
//   distribution.
// 
//   Neither the name of Texas Instruments Incorporated nor the names of
//   its contributors may be used to endorse or promote products derived
//   from this software without specific prior written permission.
// 
// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS 
// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT 
// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT 
// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, 
// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT 
// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT 
// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE 
// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
// $
//#############################################################################

//
// Included Files
//
#include "driverlib.h"
#include "device.h"
#include "board.h"
#include "c2000ware_libraries.h"

float f1 = 1.2345;
float f2 = -6.789;
unsigned int u1 = 0;
unsigned int u2 = 0;
signed int s1 = 0;
signed int s2 = 0;

//
// Main
//
void main(void)
{

    //
    // Initialize device clock and peripherals
    //
    Device_init();

    //
    // Disable pin locks and enable internal pull-ups.
    //
    Device_initGPIO();

    //
    // Initialize PIE and clear PIE registers. Disables CPU interrupts.
    //
    Interrupt_initModule();

    //
    // Initialize the PIE vector table with pointers to the shell Interrupt
    // Service Routines (ISR).
    //
    Interrupt_initVectorTable();

    //
    // PinMux and Peripheral Initialization
    //
    Board_init();

    //
    // C2000Ware Library initialization
    //
    C2000Ware_libraries_init();

    //
    // Enable Global Interrupt (INTM) and real time interrupt (DBGM)
    //
    EINT;
    ERTM;

    while(1)
    {
        u1 = (unsigned int)f1;
        u2 = (unsigned int)f2;
        s1 = (unsigned int)f1;
        s2 = (unsigned int)f2;
        
    }
}

//
// End of File
//