I2C scanner code not working on PIC18F4550

[tonkostz]

Thanks!
I am still not sure how the I2C scanner code works. After finishing i show address: EE and 112 devices found. I watch this on a LCD and not from the serial port as in the original code. Please, give me a clue what is wrong here.

[Ttelmah]

The reason I2C is not mentioned, is that this was a registered name, when
this chip was being done, and the manufacturers elected not to license
the term. TWI (Two wire interface), is a term that Quintic used to avoid
having to license using the name. The registration actually expired in 2011,
but some manufacturers just don't want to use the term....
Now 112 devices found implies the lines are not correctly going up.
How long are the wires?. Though 3.3K should work for a single device
with short wires, I suggest going quite a bit lower. Also specify the speed
on the I2C setup. SLOW=100000. How is the device connected?. Is this
all on a single board, or are you using an attached board with the chip?.
If the latter, look very carefully at how good these connections are and how
we'll smoothed the power rails actually are.

[tonkostz]

The chip is on the main board and i use a separate small board with the mcu attached to the main board. It is a single device and the wires are about 3cm long between the mcu and the chip.
Here is a picture of the whole thing with the original control board on the photo:


As soon as insert the original control board with STC mcu everything works and chip responds to commands. One more thing. On thhe original board there are no pull-up resistors on both SDA and SCL? Maybe they are using internal pull-ups in the mcu? Also the STC mcu is powered from +4V and there are 100 ohms series resistors on both SDA and SCL to the chip. QN8007 is powered from +3.3V.
I have made the following test to see what is happening.
When i disconnect both SDA and SCL from the slave chip but leave the pull-up resistors connected to the mcu. When i power on, it immediately says "Nothing found".
When SDA and SCL are connected to the chip, count is incremented at each address and in the end the number is equal to the addresses which are tried.
So the chip responds to each address or something wrong with the wiring maybe?

[tonkostz]

Here are some oscillograms from different addresses while the I2C scanner program is running. Pull-up resistors are now 2K4 to +3.3V. It seems like the chip is responding to each address or i am wrong? Blue trace is SCK and the read trace is SDA.

[Ttelmah]

OK. I suspect the scanner will not work with this.
As explained earlier, this was a bus where the sellers didn't want to pay
any licensing to use I2C. I have played with it in the past, and know
that you can use I2C drivers to talk to it OK, _But_, the bus uses active
pull up/down on the master, not open collector drives, so does not send
an ACK back from the slave. Effectively it is 'one way' I2C, with no
clock stretching, or ACK. I drove it using a software I2C, and could talk
to the chip, but doubt if the hardware will work, because the master will
not get the ACK correctly.
So, forget the bus scanner. Set your I2C configuration to FORCE_SW, and
just try sending value to the chip. I suspect you will then find it works.

[Al in Michigan]

I'm having the same problem with this chip (QN8007). This is my second go around. I first ordered the IC thru aliExpress and when they (tried 2 of 5) didn't work I suspected counterfeits so I ordered fro another Chinese dealer (the only sources I can find are Chinese). These also do not work as expected -- running simple github code. Also cannot get it to respond to an I2C ID. I found this thread SEARCHING for a way to proceed. I'll monitor & contribute if I find anything.

[Ttelmah]

That makes a lot of sense.
Thing to understand is these are obsolete chips. Over fifteen years old.
Suspect genuine sources may well have pretty much dried up, so the
supplies are largely fake.
Would explain a lot....

[Al in Michigan]

Fake devices is what I'm thinking. Usually just a simple access to any chip is not too hard, normally straight forward. I've got several hour into this with zero progress. OTOH I'm in contact with a guy in Germany who recently bought some of these from China and they're working fine. I'm pretty close to cutting bait on this.

[tonkostz]

I have finally made it work. It was very simple - just sending data to the chip and it works. Thanks to Ttelmah and all other trying to help.
I've lost too many time thinking it was a standard I2C bus and finding out why the I2C scanner was not working.
Finally, i have to mention that i had oringinal control board with differemt mcu and i was sure that the chip is working and not fake.
If anybody needs help controlling this chip, please contact me.

[Ttelmah]

Good, That was why I suggested this.
It is not I2C, just happens to be drivable as I2C, but lacks the responses
on the clock line giving ACK, which is why the scanner won't work.

[Al in Michigan]

Well mine's still not working & I could use some help. Can you offer suggestions or post a snippet of code that I can use to make contact with the chip ?

[tonkostz]

This is my code kust to initiate the chip and make it transmit at a desired frequency (107.30MHz in my case). Note that the frequency is written in two registers: CH (lower 8 bits of the 10 btin channel index) and the highest 2 bits in CH_STEP. In my case 107.30MHz channel index is 0x272 so i write 0x72 in register CH and 0x02 in register CH_STEP.

[Ttelmah]

Well done tonkostz.
It is very nice to see code with a reasonable amount of documentation.
Hopefully this will allow Al, to see if his chip will work.

Happy New Year.

[Al in Michigan]

Thanks for the code. I'll need to translate that to my world but I think I see what you're doing with the read & write sequences.

[Al in Michigan]

OK , I'm not familiar with the i2c_xxxx calls used and searching returned no info. I translated to I2C usage that I'm familiar with using ESP32 library "wire.h". QN800X_I2C_ADDRESS is 0x2b
A sanity check by anyone familiar with both appreciated,

////////////////////////WRITE////
void qn8007_write(int Reg, int val)
{
i2c_start(); beginTransmission(QN800X_I2C_ADDRESS);
i2c_write(0x56); Wire.write(Reg);
i2c_write(val); Wire.write(val);
i2c_stop(); Wire.endTransmission();
}

////////////////////////READ//////
int qn8007_read(int Reg)
{
i2c_start(); Wire.beginTransmission(QN800X_I2C_ADDRESS);
i2c_write(0x56); Wire.write(0x56);
i2c_write(Reg); Wire.write(Reg);
i2c_start(); Wire.beginTransmission(QN800X_I2C_ADDRESS);
i2c_write(0x57); Wire.write(0x57);
Wire.requestFrom(QN800X_I2C_ADDRESS, 2);
buffer = i2c_read(0); int buffer=Wire.read();
i2c_stop(); Wire.endTransmission();
return buffer; return buffer;
}