Hi,
I have started newly working with AVR microcontroller.I am using
ATmega32-A microcontroller. I have connected one external ADC(AD7798). I
want read external ADC values using SPI communication.I have tried so
much but i am not able to get ADC values. My project is I have to
generate waveform using micro controller with programmable waveform
generator. I am successfully doing this and giving this signal to
sensor. I want read sensor output given to ADC and trying to read adc
value. I have attached simple circuit diagram below. I wrote code like
this
1 | // I have initialized PORTB like this
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2 |
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3 | PORTB=0x00;
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4 | DDRB=0xBF;
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5 |
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6 | // SPI initialisation
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7 | // SPI clock rate fck/16
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8 | // SPI master
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9 | // SPI MSB first
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10 | // SPI CPOL = 1, CPHA = 1
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11 |
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12 | SPCR=0x5D;
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13 | PORTB.3 = 1;
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14 |
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15 | void main (void){
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16 |
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17 | printf("adc value :%x\n",ReadAd());
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18 |
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19 | }
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20 |
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21 | I wrote all function in another file
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22 |
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23 | #define ADC_CS PORTB.3
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24 | #define WG_CS PORTB.4
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25 | #define MOSI PORTB.5
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26 | #define MISO PINB.6
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27 | #define SCK PORTB.7
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28 |
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29 | #define ADC_CS_PIN PINB.3
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30 | #define WG_CS_PIN PINB.4
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31 |
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32 | char spi(char data)
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33 | {
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34 | //Start transmision
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35 | SPDR = data;
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36 | //Wait for transmision complete
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37 | while(!(SPSR & 0x80));
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38 | return SPDR;
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39 | }
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40 |
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41 | //Sets the waveform generator output to given phase
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42 | void SetWGPhase(unsigned int phase)
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43 | {
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44 | SPCR = 0x5A;
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45 | WG_CS = 0;
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46 | while(WG_CS_PIN);
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47 | spi(0x20);
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48 | spi(0x00);
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49 | spi((char)((phase>>8)|0xC0)); //Load into phase register 0
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50 | spi((char)(phase & 0x00FF));
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51 | WG_CS = 1;
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52 | }
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53 |
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54 | unsigned int ReadAd(void)
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55 | {
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56 | unsigned int data;
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57 | ChipSelectAd(1);
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58 | //Read data
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59 | CheckStatus(); //Wait for data ready in
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60 | adc register
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61 | spi(0x58); //Place readinstruction
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62 | in communication register
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63 | data = (spi(0xFF)<<8); //Read 8 most significant
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64 | bits from data register
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65 | data |= spi(0xFF); //Read 8 leastsignificant
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66 | bits from data register
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67 | return data;
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68 |
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69 | ChipSelectAd(0);
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70 | }
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71 |
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72 | void CheckStatus(void)
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73 | {
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74 | char adcStatus;
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75 |
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76 | do
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77 | {
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78 | (void) spi(0x40);
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79 | adcStatus = spi(0xFF);
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80 | } while((adcStatus & 0x80) > 0);
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81 | }
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82 |
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83 | void ChipSelectAd(char s)
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84 | {
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85 | if(s == 1){
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86 | PORTB.3 = 0; //Switch on AD
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87 | while(PINB.3); //Wait for chip select pin
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88 | }
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89 | else
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90 | PORTB.3 = 1; //Switch of AD
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91 | }
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I have read data sheet hundreds of times but still I am able to read ADC
value. I am confusing what mistakes I am doing. I have checked each and
every pin and I have checked ADC input pin using Oscilloscope, i am
getting 0.6V input signal. Please help me to solve this problem.
Tommarow is the deadline for this project. Please any one help me to
read ADC values.
Thanks in advance.
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