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sshahryiar
Joined: 05 May 2010
Posts: 94
Location: Dhaka, Bangladesh
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| MCP3202 12-bit Dual Channel SPI ADC Driver (Full) |
 Posted: Mon Apr 08, 2013 11:36 am |
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MCP3202.h
| Code: | #use spi(MASTER, DI=PIN_A3, DO=PIN_A2, CLK=PIN_A0, BITS=8, MSB_FIRST)
#define CS pin_A1
#define CH0_CH1_DIFF 0
#define CH1_CH0_DIFF 1
#define CH0 2
#define CH1 3
#define ADC_off 4
void MCP3202_init();
unsigned long read_ad(unsigned char ch); |
MCP3202.c
| Code: | #include "MCP3202.h"
void MCP3202_init()
{
output_low(CS);
}
unsigned long read_ad(unsigned char ch)
{
unsigned char cmd = 0;
unsigned char lowByte = 0;
unsigned char highByte = 0;
register unsigned long adcValue = 0;
switch(ch)
{
case CH0:
{
cmd = 0x80;
break;
}
case CH1:
{
cmd = 0xC0;
break;
}
case CH0_CH1_DIFF:
{
cmd = 0x00;
break;
}
case CH1_CH0_DIFF:
{
cmd = 0x40;
break;
}
default:
{
return 0;
}
}
output_low(CS);
spi_xfer(0x01);
highByte = spi_xfer(cmd);
lowByte = spi_xfer(0x00);
output_high(CS);
adcValue = make16(highByte, lowByte);
adcValue &= 0x0FFF;
return adcValue;
} |
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SShahryiar |
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sshahryiar
Joined: 05 May 2010
Posts: 94
Location: Dhaka, Bangladesh
|
| Example Code |
| Posted: Mon Apr 08, 2013 11:45 am |
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| Code: | #include <16F87.h>
#device *= 16
#fuses NOWDT, INTRC, PROTECT, CPD, PUT, NOWRT
#fuses NOMCLR, BROWNOUT, FCMEN, NOIESO, NOLVP
#use delay (clock = 8MHz)
#include <lcd420.c>
#include "MCP3202.c"
void setup();
double map(double v, float x_min, float x_max, float y_min, float y_max);
unsigned long adc_avg(short channel);
void main()
{
register float V = 0.0;
register float I = 0.0;
setup();
while(TRUE)
{
V = adc_avg(0);
V = map(V, 0, 4095, 0, 5);
I = adc_avg(1);
I = map(I, 0, 4095, 0, 5);
I = (V - I);
lcd_gotoxy(1, 1);
printf(lcd_putc, "V: %1.3f V ", V);
lcd_gotoxy(1, 2);
printf(lcd_putc, "I: %1.3f A ", I);
delay_ms(400);
};
}
void setup()
{
setup_oscillator(OSC_8MHZ);
disable_interrupts(global);
setup_WDT(WDT_off);
setup_comparator(NC_NC_NC_NC);
setup_CCP1(CCP_off);
setup_SPI(SPI_disabled);
setup_timer_0(0|0|0);
setup_timer_1(T1_disabled);
setup_timer_2(T2_disabled,255,1);
set_timer0(0);
set_timer1(0);
set_timer2(0);
MCP3202_init();
lcd_init();
lcd_putc("\f");
delay_ms(200);
}
double map(double v, float x_min, float x_max, float y_min, float y_max)
{
float m = 0.0;
m = ((y_max - y_min)/(x_max - x_min));
return (y_min + (m * (v - x_min)));
}
unsigned long adc_avg(short channel)
{
unsigned char samples = 0;
unsigned long long avg = 0;
while(samples < 64)
{
switch(channel)
{
case 0:
{
avg += read_ad(CH0);
break;
}
case 1:
{
avg += read_ad(CH1);
break;
}
}
samples++;
delay_us(4);
}
avg >>= 6;
return avg;
} |
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asmboy
Joined: 20 Nov 2007
Posts: 2128
Location: albany ny
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| Posted: Mon Apr 08, 2013 4:11 pm |
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can you explain your implementation of
map()??
i see
| Quote: |
double
Is a reserved word but is not a supported data type.
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and wonder why this function uses float math??
float is very very code space and time intensive.
is there no better way to do this ??
would integer precision not
1- be sufficient
2- be what you get anyway, after all the float grinding?
( if this compiles it will still be CCS std float anyway and 'mapped' to a narrow set of float values as it is due to limit of 2^12-1 in the call setup)
i'm puzzled by this function as presented |
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asmboy
Joined: 20 Nov 2007
Posts: 2128
Location: albany ny
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| Posted: Mon Apr 08, 2013 4:32 pm |
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since you are showing 12 bit data all the time,
and fixed scaling...
what do you get if you use:
| Code: |
unsigned int16 map( unsigned int16 inarg){
unsigned int32 t1;
t1=(unsigned int32) (inarg *501);
return (t1>>12);
}
// then with V as your 12bits
printf ("result %1.2w \r\n"', map(V));
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this is far more efficient and i believe not lacking in accuracy either |
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sshahryiar
Joined: 05 May 2010
Posts: 94
Location: Dhaka, Bangladesh
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| Regarding "map" Function |
| Posted: Mon Apr 08, 2013 10:42 pm |
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The "map" function is nothing basically new. Apart from using CCS for PIC micros I also often play with Arduinos. Arduino IDE has a built-in function called map to scale an input data range to another desired data range. It impressed me a lot and I decided to integrate it CCS too. I wrote a post for it a few months back here:
http://www.ccsinfo.com/forum/viewtopic.php?t=49501.
It may not be efficient in terms of code size but it can save a lot of time when you have to get something done easily, fast or in a segmented pattern. Imagine if you have multiple ADC inputs and you have to scale them differently from one another. In such cases map function comes handy and a programmer has to worry less for calculations. Also note a scenario in which your input-output relation is non-linear, rather like a curve. You can have them segmented in small straight line and use map for different segments to get an approximate desired output without getting your 8 bit micro to solve high order-resource consuming mathematical manipulation.
In short "map" is like a straight line equation and it finds out the dependent variable by equating the given ranges of both input and output.
Lastly if it was a reserved word for any compiler then the compiler should have given an error. I also tested it with MikroC and it gave no error just like CCS.
Thanks.
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SShahryiar |
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