I2C issues... can't get an ACK. Big demo tommorow :(

davidpk · Joined: 29 Apr 2004 Posts: 13 Location: Opelika, AL

Are you sure you didn't accidentally change the device address with your drivers? Can you look at the signals on an O'Scope?

PCM programmer · Joined: 06 Sep 2003 Posts: 21708

1. You should post a complete demo program. It doesn't have to
be much longer than what you posted, but you should show main(),
and all pre-processor statements and compiler directives.
The lines of code that you think are not important and therefore
should not be posted, could very well be the cause of your problems.

2. This chip is in a QFN package. Did you solder it to the board
yourself ? Do you know for certain that it's soldered in correctly ?
Do you know for sure that the orientation of the chip is correct ?

3. I notice you have LVP in your #fuses statement. That means
you want to use Low Voltage Programming mode. Are you really
doing that ? What programmer are you using ? How do you
keep that Pin B4 in a safe state when the programmer is not
connected ? Do you have a pull-down resistor on the pin ?
Also, according to the data sheet, LVP mode only works at 5v.
(Section 14.3) But you said your Vdd is +3.3v. Are you
removing the chip from the circuit to program it ?

blak3r · Joined: 11 Jan 2004 Posts: 45

1) I understand. The computer i was developping couldn't connect to the net so i retyped the code. Other then what i posted i set the comparators to NC_NC_NC_NC and disabled the timers.

2) I had professional solder it that's been doing rework for 30 years.

3) I had a problem with my board that it would not operate at 3.3V but would operate at voltages above 4.2V. I changed the fuses from BROWNOUT -> NOBROWNOUT and NOLVP -> LVP and that fixed the problem. I do not gurantee that B4 is held low. I'm going over to a lab now. I will change the fuse setting to NOLVP. Could this really cause an issue with my code?

Another note: using a multimeter when my i2c code is executing the multimeter reads 1.3V.
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PCM programmer · Joined: 06 Sep 2003 Posts: 21708

rnielsen · Joined: 23 Sep 2003 Posts: 852 Location: Utah

First, if you connect a meter up to a toggling signal you will see about the middle of whatever it is toggling at ie. 0v - 3.3v is about 1.3v, 1v - 5v is about 2.5v.

Second, I would remove your output_float() statements. I'm not sure if this puts the I/O into Input mode or not but they DO need to be set to be Inputs.

Third, you really need a scope to watch the signals. I use one that will capture the signal and I can then scroll to see exactly what's happening with them.

Fourth, maybe try about a 4K resistor. Who knows, maybe they need a little more 'umph' to be pulled high.

Just make sure that your compass is set at the correct address.

Ronald

ckielstra · Joined: 18 Mar 2004 Posts: 3680 Location: The Netherlands

Besides the #use delay also provide us with the #use RS232 declaration!

Are you sure the SDA and SCL pins are connected to the correct pins on the HMC6532 and not twisted?

Are you using the hardware UART for the RS-232 transmission? If yes, than this might be your problem as the PIC16F628 has the hardware Rx on RB1, the same pin you are using for SCL...... Twisted Evil