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Cogitum
Joined: 22 Mar 2012
Posts: 70
Location: France (Paris)
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| ADXL 345 and 18F66K22 NO WORKING ? |
 Posted: Tue Nov 17, 2015 9:55 pm |
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Hi,
The hardware I use is operating normally.
ADXL345 generates X, Y and Z with another program and I get to do what I want. This is not the case with the program below.
I want to generate a "pulse" to generate an interrupt (thereafter) but program generates signals of 0V and 3V for 200 for 700 uS
The pin 8 of ADXL345 is connected to pin 48 of 18F66K22 with a pull up R 10K.
COMPILER VERS 4.132
| Code: | #include <18F66K22.h>
#device adc=12
#FUSES NOWDT //No Watch Dog Timer
#FUSES WDT128 //Watch Dog Timer uses 1:128 Postscale
//#FUSES INTRC //Internal RC Osc
#FUSES NOBROWNOUT //No brownout reset
//#FUSES NOLVP //No low voltage prgming, B3(PIC16) or B5(PIC18) used for I/O
#FUSES HSH //High speed Osc, high power 16MHz-25MHz
#FUSES BBSIZ1K //1K words Boot Block size
#FUSES NOXINST //Extended set extension and Indexed Addressing mode disabled (Legacy mode)
#use delay(crystal=20M)
//!#use delay(clock=20000000)
#use rs232(baud=9600,parity=N,xmit=PIN_C6,rcv=PIN_C7)
#use i2c(Master,Fast,sda=PIN_C4,scl=PIN_C3)
#include <stdio.h>
#include <string.h>
#include <stdlib.h>
#include <math.h>
#define ACCEL_WRITE_ADDR 0XA6
#define ACCEL_READ_ADDR 0XA7
#define ACCEL_DATA_ADDR 0x32
#define ACCEL_PWRCTRL_ADDR 0x2d
#define ACCEL_MEASURE_MODE 0x08
#define ACCEL_THRESH_TAP 0x1D
#define ACCEL_TAP_AXES 0x2A
#define ACCEL_LATENT 0x22
#define ACCEL_WINDOWS 0x23
#define ACCEL_DURATION 0x21
#define ACCEL_INT_ENABLE 0x2E
#define ACCEL_INT_MAP 0x2F
#define ACCEL_INT_SOURCE 0x30
#define ACCEL_DATA_FORMAT 0x31
void main()
{
printf ("START TEST \r\n");
while(TRUE)
{
output_high(pin_G0);
// Tell the accelerometer to wake up
i2c_start();
i2c_write(ACCEL_WRITE_ADDR);
i2c_write(0X31);
//! i2c_write(0X00);// init register (scale)
i2c_write(0X3);//
i2c_stop();
I2C_start();
i2c_write(ACCEL_WRITE_ADDR);
i2c_write(ACCEL_PWRCTRL_ADDR);
i2c_write(0x08);
i2c_write(ACCEL_MEASURE_MODE);
i2c_write(ACCEL_LATENT);
i2c_write(0x50);
//!i2c_write(0x50);
i2c_write(ACCEL_WINDOWS);
i2c_write(0xFF);
i2c_write(ACCEL_DURATION);
i2c_write(0x1F);
i2c_write(ACCEL_TAP_AXES);
i2c_write(0x7);
i2c_write(ACCEL_THRESH_TAP);
i2c_write(48);
i2c_write(ACCEL_INT_SOURCE);
i2c_write(0x01);
i2c_write(ACCEL_DATA_FORMAT);
i2c_write(0x01);
i2c_write(ACCEL_INT_ENABLE);
i2c_write(0x90);
i2c_write(ACCEL_INT_MAP);
i2c_write(0x80);
I2C_stop();
output_low(pin_G0);
}
} |
Thank for your HELP |
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guy
Joined: 21 Oct 2005
Posts: 297
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| Posted: Sat Nov 21, 2015 7:00 am |
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assuming you are programming the ADXL correctly it will generate an active-high interrupt pulse of 3V because it works on ~3V. To receive this in the 5V PIC you can do either:
1. Connect the signal to the pic's COMPARATOR and set a voltage reference of <3V. This will cause a comparator interrupt.
2. Connect the signal through a resistor to the base of a transistor, and then use your existing 5V pull-up resistor for the output. This will convert the signal from 3V to 5V but it will also INVERT it. Normally it would be high, and fall when interrupt is received.
Does this help? |
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temtronic
Joined: 01 Jul 2010
Posts: 9589
Location: Greensville,Ontario
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| Posted: Sat Nov 21, 2015 9:59 am |
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'Classic' 5 volt PIC and 3 volt peripheral ?
options include
1) using a 3 volt rated PIC ( 'L' versions )
2) logic level converters between PIC and peripheral
1 is easy , 2 means more parts, chance of miswiring
Jay |
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guy
Joined: 21 Oct 2005
Posts: 297
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| Posted: Sat Nov 21, 2015 10:12 am |
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| The I2C can work on 3V pull-up resistors and then the only interface missing is the INT pins. |
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Ttelmah
Joined: 11 Mar 2010
Posts: 19967
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| Posted: Sat Nov 21, 2015 10:19 am |
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SMBUS.
You need to have pull-ups to 3.3v, and set PIC I2C to use SMBUS (this is an option in #USE I2C).
On chips that support SMBUS (this one does), it'll then reprogram the PIC I/O levels to accept the required inputs. Without this, the PIC will not see the bus as going high enough. |
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