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seyoung
Joined: 11 Nov 2016
Posts: 8
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| 4byte array convert to float |
 Posted: Fri Nov 11, 2016 10:25 am |
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| Code: |
void OPC_N2_data_read()
{
unsigned long PM_int[3] = { 0x00, };
unsigned char iobyte[3][4] = {0x38,0x95,0x86,0x42,0xd8,0xfe,0x9d,0x42,0xe3,0xb3,0x9f,0x42 };
float PM[3] = { 0x00, };
int i;
for(i = 0; i<3; i++)
{
//PM_int[i] = ((iobyte[i][3] & 0xFF) <<24);
//PM_int[i] += ((iobyte[i][2] & 0xFF) <<16);
//PM_int[i] += ((iobyte[i][1] & 0xFF) <<8);
//PM_int[i] += iobyte[i][0] & 0xFF;
PM_int[i] = ((iobyte[i][3]<<24)|(iobyte[i][2]<<16)|(iobyte[i][1]<<8)|(iobyte[i][0]));
PM[i] = *((float*)&PM_int[i]);
}
printf ("%x%x%x%x\r\n",iobyte[0][0],iobyte[0][1],iobyte[0][2],iobyte[0][3]);
printf ("%x%x%x%x\r\n",iobyte[1][0],iobyte[1][1],iobyte[1][2],iobyte[1][3]);
printf ("%x%x%x%x\r\n",iobyte[2][0],iobyte[2][1],iobyte[2][2],iobyte[2][3]);
printf ("%lx,%lx,%lx\r\n", PM_int[0],PM_int[1],PM_int[2]);
printf ("%3.5f,%3.5f,%3.5f\r\n", PM[0],PM[1],PM[2]);
} |
If i run the above code using another compiler, it will behave normally follow.
38958642
d8fe9d42
e3b39f42
42869538,429dfed8,429fb3e3
67.29144,78.99774,79.85134
However, if you compile with pcw and run it through pic18j10, you will get follow:
38958642
d8fe9d42
e3b39f42
0038,00d8,00e3
0.00000,0.00000,0.00000
I do not know where the problem is. |
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gaugeguy
Joined: 05 Apr 2011
Posts: 291
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| Posted: Fri Nov 11, 2016 10:32 am |
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You need to cast iobyte to an int32 in the expression before shifting it.
(int32)iobyte[i][3]<<24 |
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seyoung
Joined: 11 Nov 2016
Posts: 8
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| Posted: Fri Nov 11, 2016 10:37 am |
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| Code: |
PM_int[i] = (((int32)iobyte[i][3]<<24)|((int32)iobyte[i][2]<<16)|((int32)iobyte[i][1]<<8)|((int32)iobyte[i][0]));
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change and test ..
however. i receive following..
38958642
d8fe9d42
e3b39f42
9538,fed8,b3e3
0.00000,0.00000,0.00000 |
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seyoung
Joined: 11 Nov 2016
Posts: 8
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| Posted: Fri Nov 11, 2016 10:38 am |
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unsigned long PM_int[3] = { 0x00, }
is this code change like..
unsigned int32 PM_int[3] = { 0x00, } ?? |
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PCM programmer
Joined: 06 Sep 2003
Posts: 21708
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| Posted: Fri Nov 11, 2016 12:38 pm |
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I modified your program to make it work. It now outputs:
| Quote: |
38958642
d8fe9d42
e3b39f42
42869538,429dfed8,429fb3e3
67.29144,78.99774,79.85134
|
Test program:
| Code: | #include <18F46K22.h>
#fuses INTRC_IO,NOWDT,PUT,BROWNOUT
#use delay(clock=4M)
#use rs232(baud=9600, UART1, ERRORS)
// The following file has routines to convert between IEEE floating
// point format, and Microchip PIC 32-bit floating point format.
#include <ieeefloat.c>
void OPC_N2_data_read()
{
int32 PM_int[3] = {0,0,0};
unsigned char iobyte[3][4] =
{
{0x38,0x95,0x86,0x42}, // 67.29144 in IEEE format
{0xd8,0xfe,0x9d,0x42}, // 78.99774 in IEEE format
{0xe3,0xb3,0x9f,0x42} // 79.85134 in IEEE format
};
float PM[3] = {0,0,0};
int i;
for(i=0; i<3; i++)
{
PM_int[i] = (((int32)iobyte[i][3]<<24) | ((int32)iobyte[i][2]<<16) | ((int32)iobyte[i][1]<<8) | ((int32)iobyte[i][0]));
PM[i] = f_IEEEtoPIC((int32)PM_int[i]);
}
printf ("%x%x%x%x\r\n",iobyte[0][0],iobyte[0][1],iobyte[0][2],iobyte[0][3]);
printf ("%x%x%x%x\r\n",iobyte[1][0],iobyte[1][1],iobyte[1][2],iobyte[1][3]);
printf ("%x%x%x%x\r\n",iobyte[2][0],iobyte[2][1],iobyte[2][2],iobyte[2][3]);
printf ("%lx,%lx,%lx\r\n", PM_int[0],PM_int[1],PM_int[2]);
printf ("%3.5f,%3.5f,%3.5f\r\n", PM[0],PM[1],PM[2]);
}
//======================================
void main()
{
OPC_N2_data_read();
while(TRUE);
} |
These posts contain a link to the floatconv.exe program and explain
how to use it. You can use it to convert from floating point numbers
to bytes, or to Microchip format floats, or to IEEE floats, etc.
http://www.ccsinfo.com/forum/viewtopic.php?t=22336&start=1
http://www.ccsinfo.com/forum/viewtopic.php?t=50713&start=4
Example of how to use FloatConv.exe:
Start the program. Select "IEEE754 32bit". Then type the following
numbers in the boxes for Byte1 through Byte4: 42 86 95 38
The click the "Convert To Float" button. It will display 67.2914428711
in the Float box. This is correct.
This CCS FAQ page explains the Microchip floating point format,
which is used by CCS:
http://www.ccsinfo.com/faq.php?page=mchp_float_format |
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