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stoyanoff
Joined: 20 Jul 2011
Posts: 375
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| Question about I2C communication |
 Posted: Sat Jan 11, 2014 1:22 pm |
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Greetings! I'm working with a sensor through SPI interface! Sometimes my program blocks and there is no cpu reset, in spite of the WDT is running. Is it possible the SPI to cause this blockage??
Thanks!
Last edited by stoyanoff on Sun Jan 12, 2014 10:58 am; edited 1 time in total |
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temtronic
Joined: 01 Jul 2010
Posts: 9255
Location: Greensville,Ontario
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| Posted: Sat Jan 11, 2014 1:43 pm |
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historically nothing should be able to interfere with the WDT from triggering a reset, provided it really is enabled, so SPI shouldn't be a factor.
Without seeing your code, we can't tell what PIC, whether the WDT is enabled or if you've compiled in 'debug' mode instead of 'release'.
hth
jay |
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stoyanoff
Joined: 20 Jul 2011
Posts: 375
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| Question about SPI communication |
| Posted: Sun Jan 12, 2014 12:50 am |
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I'm using 24GJ64GA306, MPlab v8.93, CCS v4.134. Here are parts of my code:
| Code: |
#include <24FJ64GA306.h>
#FUSES HS,WDT_SW,WPOSTS8,PR
#use delay(clock=20M)
#use I2C(MASTER,SCL=PIN_G2,SDA=PIN_G3,FORCE_SW)
void main()
{
setup_wdt(WDT_OFF);
d=restart_cause();
delay_ms(2000);
setup_wdt(WDT_ON);
while(!StartProcedure()); //sensor init
reset_wdt();
while(1)
{
//main program
reset_wdt();
}
}
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Sometimes on power up my controller blocks and there is no reset until I don't turn off the power.
Thanks! |
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temtronic
Joined: 01 Jul 2010
Posts: 9255
Location: Greensville,Ontario
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| Posted: Sun Jan 12, 2014 6:38 am |
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I don't use the 24 series but does the '1Hz blinking LED' program work?
There's a LOT of fuses nowadays and maybe you don't have the correct ones enabled/disabled?
It can easily be a hardware issue,1Hz proves basic PIC operation.
Something in here...
StartProcedure()
...could be 'blocking' your program...
Only giving us 'parts of my code' doesn't allow anyone to copy/paste/debug.
we need more info to further help you.
jay |
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jeremiah
Joined: 20 Jul 2010
Posts: 1358
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| Posted: Sun Jan 12, 2014 7:31 am |
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| Your code shows I2C rather than SPI. I2C can indeed block if the hardware is incorrect or the software has bugs. If you really are using I2C, you should start with PCM Programmers I2C bus scanning program and see if that locks up. It's in the code library forum. |
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jeremiah
Joined: 20 Jul 2010
Posts: 1358
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| Posted: Sun Jan 12, 2014 2:11 pm |
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Stoyanoff is having trouble posting to the forums. He sent me a PM. Feel free to post any options. He can still read, but posting only goes to the preview page. I get the same forum issue from work. Can't post at all when I need to. Same browser/settings/etc. Anyways, his PM to me followed by my response:
| stoyanoff wrote: | I`m sorry! It`s I2C. I can`t write into the forum. It shows only preview but doesn`t post my messages.
So how can I prevent I2C from blockage or to force cpu reset?!
Thanks! |
It's ok, I have the exact same problem from work. *Sometimes* if I add a bunch of empty lines at the end of my post it goes through (like 5% of the time, so not really worth it). So I normally only post from home now.
First thing is you really need to verify the hardware. Try out that I2C bus poller program from the code dev forums. Preventing the I2C from blocking can really only be prevented once we know what is causing the blocking.
Some basic things:
1. Correct pullup resistors on the SDA and SCL lines (this is extremely important these are the right values).
2. PIC and I2C device are the same voltage levels (don't mix n match 3.3v and 5v devices without a level shifter inbetween.
If when you try out the bus poller program, it fails, tell me (us) what fails exactly. Does the poller program lockup? Does it work but no address gets printed? Be as specific as you can. Once we figure out the source, then we can determine which way to correct the I2C portion.
I'll post this on the forums for you. |
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stoyanoff
Joined: 20 Jul 2011
Posts: 375
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| Posted: Mon Jan 13, 2014 3:46 am |
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My controller is on 3.3, but the sensor is on 5V. I tried with level shifter, but the sensor doesn`t respond! So I`ve changed the pull-up resistors values and now it`s working but with bugs! For level shifter I user 2 MOSFET transistors as the I2C specification says.
I suppose I have to remake my schematic to work on 5V. |
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jeremiah
Joined: 20 Jul 2010
Posts: 1358
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| Posted: Mon Jan 13, 2014 8:50 am |
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| Some of the more veteran users might correct me, but I believe when making your own level shifter for I2C, you have to take care with MOSFET selection. Things like the MOSFET's capacitance and on resistance can effect it. |
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