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Gerhard
Joined: 30 Aug 2007
Posts: 144
Location: South Africa
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| Advice regarding code optimisation |
 Posted: Sat Sep 13, 2008 8:34 am |
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Hi. I am busy with a project to sample data from 2*1khz analog sources, send the samples over a 485 cable, receive and split the 2 signals again and output the analog values with a MAX519 DAC. I have the code working but the output is not very accurate and i was wondering if someone might have some ideas as to improve the quality of the output signals.
Included is the transmit and receive programs.
Transmit
| Code: | #include <16F886.H>
#fuses HS, NOWDT, NOPROTECT, NOBROWNOUT, PUT, NOLVP
#use delay(clock=20m)
#use rs232(baud=38400, xmit=PIN_C6, rcv=PIN_C7)
void setup()
{
setup_adc_ports(sAN0|sAN1);
setup_adc( ADC_CLOCK_DIV_32 );
enable_interrupts(global);
}
void read_analog();
void write_toRS232(int,int);
int ch0=0,ch1=0;
void main()
{
setup();
while(1)
{
read_analog();
write_toRS232(ch0,ch1);
}
}
void write_toRS232(cho,chi)
{
putc(cho);
putc(chi);
}
void read_analog()
{
set_adc_channel(0);
delay_us(2);
ch0=read_adc();
set_adc_channel(1);
delay_us(2);
ch1=read_adc();
} |
Recieve
| Code: | #include <16F886.H>
#fuses HS,NOWDT,NOPROTECT,BROWNOUT,PUT,NOLVP
#use delay(clock=20m)
#use i2c(Master, sda=PIN_C4, scl=PIN_C3,FORCE_HW,Fast=400000)
#use rs232(baud=38400, xmit=PIN_C6, rcv=PIN_C7)
int chan0 = 0;
int chan1 = 0;
#define MAX519_ADDRESS 0x40
#define MAX519_DATA_COMMAND_DAC0 0x00 //Set channel 0 on dual dac
#define MAX519_DATA_COMMAND_DAC1 0x01 //Set channel 1 on dual dac
#int_rda //serial interupt service routine
void serial_isr() {
if (kbhit()) { //char ready on uart to come in
chan0 = getc();
chan1 = getc();
}
}
//=========================
void max519_write_dac(int8 chan0,int8 chan1)
{
disable_interrupts(global);
i2c_start();
i2c_write(MAX519_ADDRESS);
i2c_write(MAX519_DATA_COMMAND_DAC0);
i2c_write(chan0);
i2c_write(MAX519_DATA_COMMAND_DAC1);
i2c_write(chan1);
i2c_stop();
}
void main()
{
enable_interrupts(INT_RDA); // Enable Serial Reception Interrupt
enable_interrupts(GLOBAL);
while(1)
{
enable_interrupts(GLOBAL);
chan0 = getc();
chan1 = getc();
delay_us(4);
max519_write_dac(chan0,chan1);
}
} |
As can be seen the code needs to be extremely fast as to not lose any sampled data.
Any help would be appreciated. |
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PCM programmer
Joined: 06 Sep 2003
Posts: 21708
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| Posted: Sat Sep 13, 2008 11:34 am |
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In your receiver code you are using both interrupt and non-interrupt
code to get the characters. I'm not sure how your code even works.
I suggest that you remove all interrupt code from the receiver code.
Also, in your receiver interrupt routine, you check kbhit(). That's not
necessary. When an #int_rda interrupt occurs, you automatically
have a "kbhit". The interrupt will only occur if there is a kbhit.
You don't need to check it inside the isr.
But get rid of the isr for your initial test. You don't need it.
Also remove the code that enables interrupts. |
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Gerhard
Joined: 30 Aug 2007
Posts: 144
Location: South Africa
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| Posted: Sat Sep 13, 2008 12:58 pm |
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Thanks. At least I'm learning and that explains the analog that i am reading out.
In my transmitter code i have certain time delays that the pic takes to read the ADC and to transmit the data. However in my receive data i need to only output a value once that has been read by the adc otherwise my output will differ from the input. I basically need to
reconstruct the input signals with the dac as closely as possible. Is there a way to overcome this and always read the data say at 3khz and output the data in exactly the same way? |
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