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vtrx
Joined: 11 Oct 2017
Posts: 144
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| sprintf buffer |
 Posted: Fri May 06, 2022 6:14 pm |
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I'm trying to use 'sprintf' to load a buffer with decimal numbers to show in the 7 segment module (TM1637) but I don't understand how the buffer is being loaded.
The function that displays the digits searches the table for the numbers that correspond to their decimal value.
It's 4 digits.
| Code: |
const char segmentMap[] = {
0x3f, 0x06, 0x5b, 0x4f, 0x66, 0x6d, 0x7d, 0x07, // 0-7
0x7f, 0x6f, 0x77, 0x7c, 0x39, 0x5e, 0x79, 0x71, // 8-9, A-F
0x00
};
char digitos[8];
int sec, h, m, s;
...
void Mostra_digitos(void)
{
h = (sec/3600);
m = (sec -(3600*h))/60;
s = (sec -(3600*h)-(m*60));
sprintf(digitos,"%02d%02d%02d",h,m,s);
start();
writeByte(0x40);
ask();
Stop();
Start();
writeByte(0xc0);
ask();
writeByte(segmentMap[digitos[0]]);//m
ask();
writeByte(segmentMap[digitos[1]]);//m
ask();
writeByte(segmentMap[digitos[2]]);//s
ask();
writeByte(segmentMap[digitos[3]]);//s
ask();
Stop();
}
//--- |
| Code: |
...
sec = 360;
Mostra_digitos(); |
This code snippet converts seconds into hours, and returns the correct value if using a terminal or simulator.
| Code: | h = (sec/3600);
m = (sec -(3600*h))/60;
s = (sec -(3600*h)-(m*60));
sprintf(digitos,"%02d%02d%02d",h,m,s);
... |
sec=360 returns 000600
I tried using 'sprintf' to load the buffer with digits[0]=0,digits[1]=0,digits[2]=0,digits[3]=6, digits[4]=0 and digits[5]=0 but 'sprintf' didn't load the buffer this way.
How could I do? |
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PCM programmer
Joined: 06 Sep 2003
Posts: 21708
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| Re: sprintf buffer |
| Posted: Fri May 06, 2022 8:19 pm |
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| vtrx wrote: |
int sec, h, m, s;
sec = 360;
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From a previous topic, you are using the 18F4550.
In the PCH compiler, an 'int' is an unsigned 8-bit number.
It can only go up to 255. You are trying to put 360 into an int.
This will not work. |
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PrinceNai
Joined: 31 Oct 2016
Posts: 554
Location: Montenegro
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| Posted: Fri May 06, 2022 8:26 pm |
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Was just writing this. Your declarations are not ok.
| Quote: |
int sec, h, m, s;
h = (sec/3600);
m = (sec -(3600*h))/60;
s = (sec -(3600*h)-(m*60));
|
This can't work, since you declared at least sec as a wrong type (a number between 0 and 255), than divided that by 3600 and expected to get an integer bigger than 0 from that division. Try it in Excel with the result cell formatted as a number without decimals. Always 0. sec should be int16 |
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vtrx
Joined: 11 Oct 2017
Posts: 144
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| Posted: Fri May 06, 2022 8:57 pm |
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You are really correct!
I tested the conversion code using this page.
https://www.programiz.com/c-programming/online-compiler/
| Code: | int sec, h, m, s;
printf("Input seconds: ");
scanf("%d", &sec);
h = (sec/3600);
m = (sec -(3600*h))/60;
s = (sec -(3600*h)-(m*60));
printf("H:M:S - %02d:%02d:%02d\n",h,m,s);
return 0; |
Is it necessary for h,m and s to be int16 too?
I just changed sec to int16 and it worked.
thank you all. |
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PrinceNai
Joined: 31 Oct 2016
Posts: 554
Location: Montenegro
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| Posted: Fri May 06, 2022 9:23 pm |
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| If you know the size of the result, it isn't or shouldn't be necessary. If not, you lose 3 bytes of RAM and some extra processor time by declaring them all as int16. From personal experience it is better to work with the same size of the variables. |
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