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haseeb
Joined: 27 Apr 2011
Posts: 19
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| SRF02 ranger interface via USART (Serial) |
 Posted: Tue Sep 27, 2011 5:58 am |
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Hello
Please can someone help me to get the SRF02 ranger to register correctly by sending the correct distance
in CM. At the moment it is only replying back '0' and its LED flashs according to my program loop.
First I used the ranger via I2C interface and that worked well. Now I changed that to serial interface via
changing tie the SRF02 pin 4 to zero volts.
Im using the PIC18F2620 internal OSC @ 4MHz programming in CCS compiler. Below is my small test
program. Please can someone help me to get the SRF02 ranger to register correctly by sending the correct
distance to my serial port and print that out to hypertermial.
Thanks
Haseeb
| Code: |
#include <18F2620.h>
#include <stdio.h>
#fuses INTRC_IO,NOWDT,NOPROTECT,NOLVP,NOPUT, NOPBADEN
// Set Speed to 4Mhz
#use delay(clock=4000000)
// Sonar
#use rs232(baud=9600, stop=2, parity=N, xmit=PIN_B2, rcv=PIN_C7, STREAM=Sonar)
// PC
#use rs232(baud=9600, xmit=PIN_B4, rcv=PIN_B3 ,STREAM=PC)
int range,
sonar_address = 0x00, //sonar address (factory default)
sonar_command = 0x54; //Enable Real Ranging Mode command '0x54' for...
//Result in centimeters & automatically Tx range back to...
//controller as soon as ranging is complete
void main(void)
{
delay_ms(100); //startup delay
while(true)
{
fputc(sonar_address, Sonar); //Sonar address '0'
fputc(sonar_command, Sonar); //data 0x54
while(!kbhit(Sonar)); //wait for char in USART buffer
range = fgetc(Sonar); //dump range in variable
fprintf(PC,"Range is %u cm\n\r",range);
delay_ms(250);
}
}
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temtronic
Joined: 01 Jul 2010
Posts: 9199
Location: Greensville,Ontario
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| Posted: Tue Sep 27, 2011 6:52 am |
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Two items
1) add 'errors' to the use rs232() options....
2) is the sonar module direct TTL connection or more proper RS-232 ? Does it need MAX232 or equal chips to interface? |
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ezflyr
Joined: 25 Oct 2010
Posts: 1019
Location: Tewksbury, MA
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| Posted: Tue Sep 27, 2011 7:27 am |
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Hi,
The SRF02 range finder module has a TTL serial interface, so it connects directly to the PIC serial port.
Are you sure that the module is still set to the default address of 0? The documentation implies that the address is "flashed" by the LED on power-up. A 0 address is one long flash of the LED. I don't know what you mean by "the LED flashes according to my program loop"? The SRF02 documentation does not mention that the LED also operates in a "serial receive" mode. It may, but it could also mean that your module is continually resetting?
Have you tried any other commands? A command that is totally unrelated to sonar ranging may be a good idea. Why not try command 93, and see if you can read the single byte firmware version?
Good Luck,
John |
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