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kender
Joined: 09 Aug 2004
Posts: 768
Location: Silicon Valley
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| Problems reading DS1307 |
 Posted: Tue Aug 24, 2004 1:55 pm |
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Colleagues,
When reading from DS1307 RTC I'm getting this artifact. Evey other packet I receive is identical and is also garbage. Could you take a look at the code and the output and tell me what's wrong?
Thanks,
Nick
| Code: |
#include "test13.h"
void main()
{
setup_adc_ports(NO_ANALOGS);
setup_adc(ADC_OFF);
setup_psp(PSP_DISABLED);
setup_counters(RTCC_INTERNAL,RTCC_DIV_1);
setup_timer_1(T1_DISABLED);
setup_timer_2(T2_DISABLED,0,1);
enable_interrupts(INT_RDA);
enable_interrupts(GLOBAL);
printf("start\n\r");
while(1)
{
// writer the read address for the seconds register (0x00)
do i2c_start();
while (1 == i2c_write(0b11010000)); // poll for ack
printf("wr ack\n\r");
i2c_write(0x00); // seconds address
// read the seconds from the RTC and output them to RS232
do i2c_start();
while (1 == i2c_write(0b11010001)); // poll for ack
printf("rd ack\n\r");
printf("0x%X ", i2c_read()); // read the seconds
printf("0x%X ", i2c_read()); // read the minues
printf("0x%X\n\r", i2c_read()); // read the hours
i2c_stop(); // end of transaction
delay_ms(2000);
}
}
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Header file:
| Code: |
#include <18F452.h>
// #device ICD=TRUE
#device adc=10
#use delay(clock=12800000)
#fuses NOWDT,WDT128,HS, NOPROTECT, NOOSCSEN, BROWNOUT, BORV20, NOPUT, STVREN, NODEBUG, NOWRT, NOWRTD, NOWRTB, NOWRTC, NOCPD, NOCPB, NOEBTR, NOEBTRB //, LVP
#use rs232(baud=19200,parity=N,xmit=PIN_C6,rcv=PIN_C7,bits=8)
#use i2c(Master,Fast,sda=PIN_C4,scl=PIN_C3)
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Output:
| Code: |
0x51 0x54 0x20 // OK
0x03 0xFF 0xFF // gardbage
0x55 0x54 0x20 // OK
0x03 0xFF 0xFF // garbage
0x59 0x54 0x20 // OK
0x03 0xFF 0xFF // garbage
0x03 0x55 0x20 // OK, minutes change
0x03 0xFF 0xFF // garbage
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Nick
Guest
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| Posted: Tue Aug 24, 2004 1:59 pm |
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Have you hooked up your 3v battery? is the connection loose? Thats how I usually end up getting garbage over my DS1307. I even made a check for it to tell me what was the problem since I'm using a soldierless bread board and connections arnt that great.
Nick |
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PCM programmer
Joined: 06 Sep 2003
Posts: 21708
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| Posted: Tue Aug 24, 2004 2:03 pm |
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I didn't check your entire code in detail, but I see two things:
1. The last call to i2c_read(), in a series of calls, must have a 0
parameter. This does a "NAK" instead of an ACK. This is part
of the i2c specification.
Example:
i2c_read();
i2c_read();
i2c_read(0); // Last call does a NAK
2. If it was me, I would disable interrupts while doing the i2c operations. |
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kender
Joined: 09 Aug 2004
Posts: 768
Location: Silicon Valley
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| Posted: Tue Aug 24, 2004 2:04 pm |
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My battery connection and battry voltage look OK. Also, both PIC and DS1307 are running of 5V regulator. I might be wrong, but I think that in this case the 3V battery doesn't have a lot of influence. Thanks for the tip though.
Nick |
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kender
Joined: 09 Aug 2004
Posts: 768
Location: Silicon Valley
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| Posted: Tue Aug 24, 2004 2:08 pm |
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i2c_read(0) worked. The data is valid all the time now.
Thank you!
Nick |
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Guest
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| Posted: Tue Aug 24, 2004 3:15 pm |
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| kender wrote: | | I might be wrong, but I think that in this case the 3V battery doesn't have a lot of influence. |
IME, the DS1307 will not function at all without the 3V battery and the 32 kHz xtal connected. Glad you got it going though. |
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kender
Joined: 09 Aug 2004
Posts: 768
Location: Silicon Valley
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| Posted: Tue Aug 24, 2004 3:20 pm |
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Well, I have just removed the battery without turning off 5V, reset the PIC, and DS1307 was outputing the correct data.
Nick |
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ximo
Joined: 30 Sep 2004
Posts: 2
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| ds1307 driver |
| Posted: Thu Oct 07, 2004 9:03 am |
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this is my driver for the ds1307 and function very good with 16f877a and 18f8720:
| Code: |
// first configure the i2c
#use I2C(MASTER, SDA=PIN_C4, SCL=PIN_C3, RESTART_WDT, FAST)
void get_rtc_time(){
int i;
i2c_start();
i2c_write(code_escribe);
i2c_write(0);
i2c_start();
i2c_write(code_escribe | 1);
for (i=0;i<sizeof(rtc);i++)
rtc[i]=i2c_read(i<sizeof(rtc)-1); //rtc is a array with the read
i2c_stop();
}
void set_rtc_time(){
int i;
i2c_start();
i2c_write(code_escribe);
i2c_write(0);
for(i=1;i<sizeof(config);i++)
i2c_write(config[i]); //config is a array with the hour etc...
i2c_stop();
} |
[/code] |
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asmallri
Joined: 12 Aug 2004
Posts: 1635
Location: Perth, Australia
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| Posted: Thu Oct 07, 2004 9:23 am |
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| kender wrote: | Well, I have just removed the battery without turning off 5V, reset the PIC, and DS1307 was outputing the correct data.
Nick |
That is just luck. When you actually try using it in the field it WILL crash. It is possible to use the DS1307 without a battery but in this case you need to pull the +battery input pin to ground via a resistor. It may also work pulling it to plus 5 but that is not how I use the device. The reason it will crash without this is because it is a smart little bugger. If it sees the battery pin is a higher potential that the +5v rail, it assumes the +5v rail is failing and shuts down all interfaces to save power. And guess what, sooner or later the +battery terminal will float higher than the +5V rail - maybe when a cat comes in the room, or it starts raining outside or just for the hell of it. It is dead easy to test. I spent three weeks chasing this intermittent crash problem.
Last edited by asmallri on Thu Oct 07, 2004 5:49 pm; edited 1 time in total |
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Ttelmah
Guest
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| Re: Problems reading DS1307 |
| Posted: Thu Oct 07, 2004 10:05 am |
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| kender wrote: | Colleagues,
When reading from DS1307 RTC I'm getting this artifact. Evey other packet I receive is identical and is also garbage. Could you take a look at the code and the output and tell me what's wrong?
Thanks,
Nick
| Code: |
#include "test13.h"
void main()
{
setup_adc_ports(NO_ANALOGS);
setup_adc(ADC_OFF);
setup_psp(PSP_DISABLED);
setup_counters(RTCC_INTERNAL,RTCC_DIV_1);
setup_timer_1(T1_DISABLED);
setup_timer_2(T2_DISABLED,0,1);
enable_interrupts(INT_RDA);
enable_interrupts(GLOBAL);
printf("start\n\r");
while(1)
{
// writer the read address for the seconds register (0x00)
do i2c_start();
while (1 == i2c_write(0b11010000)); // poll for ack
printf("wr ack\n\r");
i2c_write(0x00); // seconds address
// read the seconds from the RTC and output them to RS232
do i2c_start();
while (1 == i2c_write(0b11010001)); // poll for ack
printf("rd ack\n\r");
printf("0x%X ", i2c_read()); // read the seconds
printf("0x%X ", i2c_read()); // read the minues
printf("0x%X\n\r", i2c_read()); // read the hours
i2c_stop(); // end of transaction
delay_ms(2000);
}
}
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Header file:
| Code: |
#include <18F452.h>
// #device ICD=TRUE
#device adc=10
#use delay(clock=12800000)
#fuses NOWDT,WDT128,HS, NOPROTECT, NOOSCSEN, BROWNOUT, BORV20, NOPUT, STVREN, NODEBUG, NOWRT, NOWRTD, NOWRTB, NOWRTC, NOCPD, NOCPB, NOEBTR, NOEBTRB //, LVP
#use rs232(baud=19200,parity=N,xmit=PIN_C6,rcv=PIN_C7,bits=8)
#use i2c(Master,Fast,sda=PIN_C4,scl=PIN_C3)
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Output:
| Code: |
0x51 0x54 0x20 // OK
0x03 0xFF 0xFF // gardbage
0x55 0x54 0x20 // OK
0x03 0xFF 0xFF // garbage
0x59 0x54 0x20 // OK
0x03 0xFF 0xFF // garbage
0x03 0x55 0x20 // OK, minutes change
0x03 0xFF 0xFF // garbage
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I have used the 1307, without problems, but have allways 'stopped' each transaction, rather than using a repeated start, and used the 'NACK', on the last byte before stopping. I use:
| Code: |
/* I2C address for chip, including direction flag */
#define CADDRWR 0xD0
#define CADDRRD 0xD1
#define NACK 0
I2C_START();
WHILE (I2C_WRITE(CADDRWR));
I2C_WRITE(0); /* set address to 0 */
I2C_STOP();
I2C_START();
WHILE (I2C_WRITE(CADDRRD));
clock.secs=I2C_READ();
clock.mins=I2C_READ() & 0x7F;
clock.hours=I2C_READ() & 0x3F;
clock.dayofweek=I2C_READ() & 7; /* day of week */
clock.dayofmnth=I2C_READ() & 0x3F; /* day of month */
clock.month=I2C_READ() & 0x1f; /* month */
clock.year=I2C_READ(NACK); /* Year, and finish */
I2C_STOP();
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I suspect your problem is not using the 'NACK', on the last transaction. The data sheet, specifically says 'the DS1307, _must_ receive a NACK, to terminate a read'.
Best Wishes |
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Mark
Joined: 07 Sep 2003
Posts: 2838
Location: Atlanta, GA
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| Posted: Thu Oct 07, 2004 10:18 am |
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| Note that this post is old and the guy solved his problem. Someone was just posting their driver code |
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Ttelmah
Guest
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| Posted: Thu Oct 07, 2004 2:17 pm |
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| Mark wrote: | | Note that this post is old and the guy solved his problem. Someone was just posting their driver code |
Yes.
For some reason, the post appeared at the head of the list as a single 'new' post (no 'driver code' visible), so I replied.
After I had replied, the 'hread' became visible.
I suspect there was a hiccup in the board somewhere.
Best Wishes |
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