receiving data on pic16F from an accelerometer MPU6050

[AKA TENDO]

[temtronic]

some comments....

1st, you need to add SMBUS to the #use I2C(.... options.... ) though you should really have 5V<>3V interface logic translators.

2nd, relocate ALL 'math' operations from inside the I2C operations

3rd, add ERRORS to the #USE RS232(...options....)

4th, add PUT to the #FUSES list

[AKA TENDO]

[temtronic]

SMBUS changes the accepted voltages for 'high'(1) and 'low'(0) on the I2C pins. You may have to lower the I2C bus pullup resistor values. Typically 3k3 for 3volt bus.
Also set the I2C speed option to SLOW. Once you get the code running 100%, THEN try the 'FAST' option.

If that doesn't get you 100% proper data, then you need to add 'logic level translator' devices between the PIC I2C bus and the MPU8050 I2C bus. The other alternative would be to use a 16LF877 and use a VDD=3 volts.

PUT is Power Up Timer. It's used to ensure the PIC powers up in a known sequence,so that it reliably works.

ERRORS adds a small amount of code to prevent the PIC HW UART from 'locking up' from data coming in (say from a PC) before the PIC can process it. The HW UART only has a 2 byte buffer, so if your program doesn't read and clear the buffer before a 3rd character comes in, the PIC will 'freeze' (stop working).

[Ttelmah]

You need to understand that you are trying to do something that is not
likely to ever work 100% reliably.

You have a 3.3v gyro chip trying to talk to a 5v PIC via I2C. Now the PIC
'properly' implements I2C. I2C has a Vih (input high voltage, when running
off 5v), of 3.5v. Problem is that the 3.3v device only supports having it's pull
up resistors go to 3.3v, so the bus does not go high enough to reliably be
seen as high by the PIC. Now the Arduino does not actually use I2C input
buffers, so can get away with this, but the PIC can't. The SMBUS
option should turn down the required Vih voltage, but it is a feature that
has varying efficacy on different PIC's. Yours is a very old chip, and I know
a lot of these do not properly implement the SMBUS option.

The 'correct' way to do what you want is to either use a 3.3v PIC (and it
is worth saying that most of these will run a lot faster, and have more RAM/
ROM than your current chip), or use a hardware level translator.

You are fighting a war with incorrect hardware, and really need to rethink
how you are trying to work.

[temtronic]

here's one example of what you need

https://universal-solder.ca/product/2-channel-level-converter-3-3v-5v-with-on-board-3-3v-ldo/

to PROPERLY interface your 3v module to your 5v PIC.

At that price it's not worth buying the pieces and soldering !
I understand that different parts of the World have 'supply issues' but as Mr. T points out ...you will NEVER get what you have to work 100% reliably.

NO amount of code,however 'clever', can cure the basic hardware problem.

[Ttelmah]

As a comment, there is one other way to get round the problem.
Instead of using the hardware I2C, choose two pins on your PIC that
have TTL input buffers, and use software I2C on these pins instead of
using the hardware port.

[temtronic]

DOH !

Perfect SOLUTION, providing he can swap 4 pins !!

Since the project is to 'level a plank using 4 actuators', it's easily done using SW I2C.

[AKA TENDO]

Hi all, thank you for your answers. I really keep what you all say in my mind but the thing is that my project work properly like i did. I guess all you said were supposed to help me and it will! but i think the PUT, ERRORS, SLOW, etc... are optional and it will ensure that my PIC won't have any problems one day, but i tried my project today with my current code and one actuator and it worked almost perfectly. I just need to reduce more the delay (I've kept 500ms). So I'm going to add all that you said in purpose to have a better code. However, for hardware part maybe i haven't explained properly my situation with the PIC, but there are actually no problems with the I2C. If i have understood correctly what you said, should i understand that my Bus can work even without all the options and the 3V interface you were talking about but it can cause some issues?

[temtronic]

re:

[AKA TENDO]

[Ttelmah]

'ERRORS', shoukd always be used when using the hardware UART, unless
you add your own error trapping and recovery to the ISR. Not using it
is criminal/stupid. I have a personal 'moan' that a lot of the older CCS
examples don't use it. However if you look, these are very old and date
back to before CCS actually got this working right...
Use it. It really should be the default behaviour by the #USE

'PUT' in this case probably doesn't matter, but would if for example you
tried to send serial data right after the boot without any delay. Get in
the habit of using this for reliability.

[AKA TENDO]

[Ttelmah]

Because that is what 'ERRORS' applies to.

[AKA TENDO]