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scanan
Joined: 13 Aug 2004
Posts: 59
Location: Turkey
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| [SOLVED] i2c problem with PIC18F86K22 |
 Posted: Thu Sep 22, 2016 4:18 am |
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Hello,
I have questions about i2c on PIC18F86K22,
I am using ccs 5.058 compiler.
My code snippets are as below
| Code: |
#define EEPROM_SDA PIN_C4
#define EEPROM_SCL PIN_C3
#use i2c(master, sda=EEPROM_SDA, scl=EEPROM_SCL,FORCE_SW)//,FAST=400000)
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this works fine
but when I change to
| Code: |
#define EEPROM_SDA PIN_C4
#define EEPROM_SCL PIN_C3
#use i2c(master, sda=EEPROM_SDA, scl=EEPROM_SCL,FORCE_HW)//,FAST=400000)
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It stops working, what could be the problem ?
PIN C3 and C4 are hardware i2c. Why ccs make problems when forced to hardware ? Any suggestions?
cheers
_________________
Dr Suleyman CANAN
R&D Electronic Engineer
https://suleymancanan.wordpress.com
Do whatever you do with amateur spirit -
But always feel professional.
Last edited by scanan on Fri Sep 23, 2016 8:41 am; edited 1 time in total |
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temtronic
Joined: 01 Jul 2010
Posts: 9246
Location: Greensville,Ontario
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| Posted: Thu Sep 22, 2016 5:03 am |
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As shown, those 2 lines of code won't be the problem.
A small program that shows it 'stopping' is needed ...
What CAN cause it to 'stop' is having the I2C ISR enabled without a handler.
Download and run PCM P's I2C scanner program from the code library, see what happens.
Also it could be incorrect I2C bus resistors.
You need to show us more code...
Jay |
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Ttelmah
Joined: 11 Mar 2010
Posts: 19552
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| Posted: Thu Sep 22, 2016 7:02 am |
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Two important differences will apply when you switch to hardware.
First the input thresholds to the PIC will change. C3 & C4, running using the software I2C, will accept as a 'high', 2v, with the hardware, the high level will switch to 0.8*Vdd.
Second the speed may well increase. Since you are not actually specifying the speed.
The response to both of these then depends on your bus resistors, and the device attached. Remember at 3.3v the resistor needs to be smaller than on a 5v bus. |
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scanan
Joined: 13 Aug 2004
Posts: 59
Location: Turkey
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| Posted: Fri Sep 23, 2016 1:24 am |
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Here some code
| Code: |
#include <18F86K22.h>
#device adc=8
#include "..\libs\elf-2416.c"
#FUSES PLLEN,VREGSLEEP,INTRC_HP,SOSC_DIG,NOXINST,INTRC_IO,NOFCMEN,NOIESO //1
#FUSES PUT,NOBROWNOUT,NOWDT //2
#FUSES MSSPMSK7,NOMCLR //3
#FUSES NOSTVREN,BBSIZ2K,NODEBUG //4
#FUSES NOPROTECT,NOCPB,NOCPD //5
#FUSES NOWRT,NOWRTC,NOWRTB,NOWRTD, //6
#FUSES NOEBTR,NOEBTRB //7
#use delay(clock=64000000)
#use rs232(baud=57600,parity=N,xmit=PIN_C6,rcv=PIN_C7,bits=8,ERRORS)
#define EEPROM_SDA PIN_C4
#define EEPROM_SCL PIN_C3
#use i2c(master, sda=EEPROM_SDA, scl=EEPROM_SCL,FORCE_HW)
void main()
{
char data,i;
setup_wdt(WDT_OFF);
setup_adc_ports(NO_ANALOGS|VSS_VDD);
setup_adc(ADC_OFF);
setup_psp(PSP_DISABLED);
setup_spi(SPI_SS_DISABLED);
setup_timer_0(RTCC_INTERNAL|RTCC_DIV_128|RTCC_8_BIT);// TIMER0
setup_timer_1(T1_INTERNAL|T1_DIV_BY_2);
setup_timer_2(T2_DISABLED,0,1);
setup_timer_3(T3_DISABLED|T3_DIV_BY_1);
setup_comparator(NC_NC_NC_NC);
setup_vref(FALSE);
setup_low_volt_detect(FALSE);
setup_oscillator(OSC_16MHZ|OSC_PLL_ON);
output_a(0x00);
output_b(0x00);
output_c(0x00);
output_d(0x00);
output_e(0x00);
output_f(0x01);
output_g(0x00);
set_tris_a(0x80);
set_tris_b(0xff);
set_tris_c(0x97);
set_tris_d(0x00);
set_tris_e(0x00);
set_tris_f(0x00);
set_tris_g(0x00);
set_tris_h(0x00);
set_tris_j(0x00);
EXT_INT_EDGE(0,L_TO_H);
enable_interrupts(INT_EXT);
enable_interrupts(INT_TIMER0); // ENABLE TIMER0
enable_interrupts(INT_TIMER1); // ENABLE TIMER1
enable_interrupts(GLOBAL);
do{
for(i=0;i<128;i++)
{
data=read_ext_eeprom(i);
printf("%x ",data);
}
}while(1==1);
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this code is just to test the eeprom.
when the i2c is defined for hadware the program hang in the for loop, when used as software i2c it works corectly
the resistor used are 4K7
_________________
Dr Suleyman CANAN
R&D Electronic Engineer
https://suleymancanan.wordpress.com
Do whatever you do with amateur spirit -
But always feel professional. |
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Ttelmah
Joined: 11 Mar 2010
Posts: 19552
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| Posted: Fri Sep 23, 2016 2:03 am |
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This line is wrong:
setup_spi(SPI_SS_DISABLED);
This enables the SPI, and disables 'slave select'.
The correct line is:
setup_spi(FALSE);
This could be interfering with the I2C hardware (since it is the same peripheral....).
4K7R, is too large for a 3.3v I2C. It's a 'typical' value for a short 5v bus, but a bit large even for this, unless capacitance is very low. The line must pull up to the Vih level, within 300nSec for a fast mode device. Assuming a bus capacitance of perhaps 100pF (input pins on both chips, trace between etc.). Gives Rp Max at about 3.8KR, and Rp Min at about 800R. Suggest 1K5R.
You enable INT_EXT, but set the pin for this to an output.
The code won't work without interrupt handlers for the three enabled interrupts.
Both I2C pins should be set as inputs if you are manually setting the TRIS. You have C4 set as output. Wrong. Data sheet section 21.4:
"The user must configure these pins as inputs by setting
the associated TRIS bits." |
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