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Registered Member #14
Joined: Thu Feb 02 2006, 01:04PM
Location: Prato/italy
Posts: 383
As a first step in building a datalogging anemometer i need to inferface DS1307 real-time clock with PIC16F88 by I2C in picbasic.
I am simulating a simple circuit with an LCD connected to the PIC and the clock connected to PORTB.6 (SDA) and PORTB.7 (SCL) using software I2C. But the reading procedure gives only random garbage.
What do you think?
'****************************************************************
'* Name : UNTITLED.BAS *
'* Author : Jonathan FIlippi *
'* Notice : Copyright (c) 2009 CC free license *
'* : All Rights Reserved *
'* Date : 30/11/2009 *
'* Version : 1.0 *
'* Notes : *
'* : *
'****************************************************************
ANSEL = %00000000
TRISA = %00000000
TRISB = %00000000
PORTA = %00000000
PORTB = %00000000
DEFINE OSC 20 'crystal oscillator f = 20MHz
Define LCD_BITS 4 'Set LCD Bus Size (4 or 8)
DEFINE LCD_DREG PORTB ' Set data pin of LCD to PORTB
DEFINE LCD_DBIT 0 ' PORTB.0-PORTB.3
DEFINE LCD_RSREG PORTB ' Set RS bit of LCD to PORTA
DEFINE LCD_RSBIT 4 ' PORTA.0
DEFINE LCD_EREG PORTB ' Set E bit of LCD to PORTA
DEFINE LCD_EBIT 5 ' PORTA.1
DEFINE LCD_LINES 2 ' 2 Lines LCD
'DEFINE I2C_SLOW 1
'DEFINE I2C_HOLD 1
SYMBOL SDA = PORTB.6
SYMBOL SCL = PORTB.7
SECS var byte
MINS var byte
HOURS var byte
DAY var byte
DATE var byte
MONTH var byte
YEAR var byte
CTRL var BYTE
SECS = 0
MINS = 30
HOURS = 12
DAY = 1
DATE = 1
MONTH = 1
YEAR = 09
CTRL = $90
PORTA.0 = 1
PORTA.1 = 1
LCDOUT $FE,1
'lettura dell' ora
pause 500
skp:
I2CREAD SDA,SCL,$D0,$00,[SECS,MINS,HOURS,DAY,DATE,MONTH,YEAR,CTRL]
pause 1000
LCDOUT $FE,$80,"T:",#SECS," ",#MINS," ",#HOURS," ",#CTRL," "
goto skp:
Registered Member #56
Joined: Thu Feb 09 2006, 05:02AM
Location: Southern Califorina, USA
Posts: 2445
You might also want to look at what data types are used by the ds1307, sometimes the little things like lsb first or msb first, two's compliment, etc, can throw you off.
Usually my system for interfacing a new part is to look for a register that has a known value (usually there is a device id or the likes) and looking at the value read back in binary--and then looking for the above issues.
Registered Member #14
Joined: Thu Feb 02 2006, 01:04PM
Location: Prato/italy
Posts: 383
SOLVED!! It was two problems:
1) the I2CREAD/WRITE command must use variables instead of constants, it screws up the reading/writing 2) the data ins in BCD format (least significant bits are the units, bit4-6 the decade)
next step is to implement FAT SD writing and a workable interface
UPDATE:
Also it was the use of "analog" pull'up resistors in simulation that screwed up the things!
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Problem interfacing DS1307 real-time clock with PIC16F88
