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Message |
octomescu
Joined: 10 Jan 2011
Posts: 5
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| PIC16F877 with AD7730 |
 Posted: Mon Jan 10, 2011 9:57 am |
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I want to realize an electronic scale and AD7730 or LTC2400 and PIC16F877. Please if you can help me with a script for CCS, such as connecting the output AD7730 / LTC2400 to PIC16F877. I found this driver but do not know how to adapt it:
| Code: |
int32 Read_A2D(void)
{
int32 A2D_COUNTS;
int i;
output_high(A2D_SCLK);
delay_us(100);
output_high(A2D_CSI);
output_low(A2D_SCLK);
output_low(A2D_CSI);
while((input(A2D_SDO))==1); //wait for /EOC to go low...
for(i=4;i>0;i--) //I don't need to use these first 4 bits
{
output_high(A2D_SCLK);
delay_us(5);
output_low(A2D_SCLK);
delay_us(5);
}
for(i=20;i>0;i--) //Set i = number of bits to read
{
output_high(A2D_SCLK);
delay_us(5);
shift_left(&A2D_COUNTS,4,input(A2D_SDO));
output_low(A2D_SCLK);
delay_us(5);
}
output_high(A2D_CSI);
return A2D_COUNTS;
}
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Thank you very much. |
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naduran
Joined: 18 Sep 2011
Posts: 2
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| Plese |
| Posted: Tue Sep 20, 2011 4:33 am |
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Please, how to use this source. I want it to meet the PIC16F876A.
Thank you very much |
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asmboy
Joined: 20 Nov 2007
Posts: 2128
Location: albany ny
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| Posted: Tue Sep 20, 2011 4:14 pm |
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for a start you want to DEFINE the control pins - as they connect to your pic
for example:
| Code: |
#DEFINE A2D_SCLK PIN_B0
#define A2D_CSI PIN_B1
#define A2D_CSI PIN_B2
#define A2D_SDO PIN_B3
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and decide if you need to use fast i/o - then do some set_tris() etc etc
in short - make some hardware decisions and tell your pic code about them
hint: you may need a weak pullup resistor on the A2D_SDO line too |
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naduran
Joined: 18 Sep 2011
Posts: 2
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| ADC LTC2400 ... |
| Posted: Wed Sep 21, 2011 3:52 am |
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I tried to apply this code:
| Code: |
#include "16F876A.H"
#fuses HS,NOWDT,PUT,BROWNOUT,NOPROTECT,NOLVP
#use delay(clock=16000000,restart_wdt)
//#use delay(clock=16000000)
//#use rs232(baud=9600, xmit=PIN_C6, rcv=PIN_C7)
#use rs232(baud=9600, UART1)
#define LTC_CS PIN_A0 // LTC2400 pin 5
#define LTC_SCK PIN_A2 // LTC2400 pin 7
#define LTC_SDO PIN_A3 // LTC2400 pin 6
#byte CMCON0 = 0x19
int32 variabila1=0;
unsigned int ADCBuffer[3];
//float rezultat = 0;
int32 rezultat = 0;
float Vref = 4.0962;
//float Vref = 5.0;
#define FULLSCALE 16777216 // 2^24
int1 ltc_clock()
{
int1 in=0;
output_high(LTC_SCK);
in=input(LTC_SDO);
delay_ms(5);
output_low(LTC_SCK);
delay_ms(5);
return(in);
}
void LTC_2400_read()
{
unsigned int i=0;
output_low(LTC_SCK);
output_low(LTC_CS);
delay_ms(70);
ltc_clock();
ltc_clock();
ltc_clock();
ltc_clock();
ADCbuffer[0]=0;
ADCbuffer[1]=0;
ADCbuffer[2]=0;
for (i = 1; i <= 24; i++) shift_left(ADCbuffer,3,ltc_clock());
output_high(LTC_CS);
delay_ms(50);
variabila1 = make32(ADCBuffer[2],ADCBuffer[1],ADCBuffer[0]);
}
void main()
{
disable_interrupts(GLOBAL);
CMCON0=7;
setup_ccp1(CCP_OFF);
setup_timer_2(T2_DISABLED,0,1);
delay_ms(10);
output_high(LTC_CS);
while(TRUE)
{
LTC_2400_read();
rezultat = (int32)variabila1 / Vref; // / FULLSCALE;
printf("%Lu \r\n", rezultat);
delay_ms(250);
}
}
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I put the LTC2400 input to GND, we next result in HyperTerminal:
4095752
15
4095779
91
29
4095785
4095775
4095789
4095788
4095752
5
4095780
66
79
83
16
4095762
21
4095790
48
3
I put the LTC2400 input to Vcc (5V), we have the following result:
4095793
4095757
4095747
43
54
4095726
4095769
1
11
56
86
120
4095688
7
45
7
37
4095739
I do not understand the cause of this instability.
Thank you. |
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asmboy
Joined: 20 Nov 2007
Posts: 2128
Location: albany ny
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| Posted: Wed Sep 21, 2011 7:39 am |
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whats your schematic ???
how is the ADC connected to what model PIC and
your measurement source?
does the LTC part require a weak pull up resistor on SDO ??
how are you managing the WDT ??
and with a char array defined for adcbuffer - THIS LOOKS very ODD indeed
shift_left(ADCbuffer,3,ltc_clock()); |
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octomescu
Joined: 10 Jan 2011
Posts: 5
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| Posted: Wed Sep 21, 2011 8:09 am |
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My schematic is:
Are already blocked. I do not know what to do.  |
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asmboy
Joined: 20 Nov 2007
Posts: 2128
Location: albany ny
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octomescu
Joined: 10 Jan 2011
Posts: 5
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| Posted: Wed Sep 21, 2011 9:07 am |
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Yes ok, but do not understand why not work with 16F876. I looked in the data sheet, but do not understand much.  |
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asmboy
Joined: 20 Nov 2007
Posts: 2128
Location: albany ny
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| Posted: Wed Sep 21, 2011 2:42 pm |
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have you tried putting a 5 k ohm - 1 turn trim pot from Vcc 5v to ground and running the wiper to the input of the ADC so you can set precise 1/2 vcc etc values ??
also this mixed casting line
| Code: |
rezultat = (int32)variabila1 / Vref; // / FULLSCALE;
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is just more uncertainty
why not try
just printing out variabila1 instead of doing the divide by float stuff ??
my first rule of "project not working":
MAKE IT AS SIMPLE as possible - to be sure the hardware works as intended.
you are at an extra disadvantage because you copied other code
other than writing it yourself from scratch.
also THIS:
you are ONLY clocking out 28 bits of a 32 bit total 'word'
also you ignore the EOC bit - but please read bottom of page 11 of data sheet starting with:
| Quote: |
In order to shift the conversion result out of the device, CS
must first be driven LOW. EOC is seen at the SDO pin of the
device once CS is pulled LOW. EOC changes real time from
HIGH to LOW at the completion of a conversion. This
signal may be used as an interrupt for an external
microcontroller. Bit 31 (EOC) can be captured on the first
rising edge of SCK. Bit 30 is shifted out of the device on the
first falling edge of SCK. The final data bit (Bit 0) is shifted
out on the falling edge of the 31st SCK and may be latched
on the rising edge of the 32nd SCK pulse. On the falling
edge of the 32nd SCK pulse, SDO goes HIGH indicating a
new conversion cycle has been initiated. This bit serves as
EOC (Bit 31) for the next conversion cycle. Table 2 summarizes
the output data format.
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i would write this driver to in a whole different way.
to make sure a conversion is ready and kosher,
also from the data sheet-
| Quote: |
Bit 31 (first output bit) is the end of conversion (EOC)
indicator. This bit is available at the SDO pin during the
conversion and sleep states whenever the CS pin is LOW.
This bit is HIGH during the conversion and goes LOW
when the conversion is complete.
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i would check the SDO line state before even starting a readout - and then read all 32 bits before raising not_cs - but that just me - striving for completeness ;-)) |
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