These are the proper read and write addresses for the module. So for the reported 0x17, Wire believes it to be 0x2E. However, the scanner sketch passes raw unshifted address. Twi_slarw |= address >1) // Wire lib shifts back left for IO build sla+w, slave device address + w bit The Wire lib then shifts it left with 1 for a read, or 0 for a write before sending it out.:
Normally the device address is shifted right one bit before passing it to the Wire.beginTransmission(address) method. Just a note: The scanner sketch miss-reports the device address. I can't get closer and stay in focus.ġ of the wave forms while the scanner sketch is running. Any chance of posting a photo of your setup?ġ of the set-up. What size cap must be applied in addition and where? All components are surface-mount technology. For this current situation, the supply is the UNO board itself, and the module has 4.7uf and 0.01uf caps from the supply to ground, on board. In fact all the wires (there is no CLK~ or OE wire) from the board go to the breadboard and they are also about an inch long. The output wire - the CLK signal - goes to the scope only. Even if you send the same code, Wire.endTransmission()should not return an error. Another almost identical program sets it to the lowest frequency. I would add extra decoupling capacitors to the supply. Where are the output wires going to? Maybe this is causing interference that is being picked up. Only when you power it down will it change. Therefore if you run the code again it will not change. That code will only set the modules output frequency to one value once per run only. The problem is simply that sometimes the module's output frequency doesn't change. I have a scope and DMMs and can do some soldering. I thought the problem might be the actual data values being sent, but the tests do not fail consistently. I have talked to several others about this problem, but they seem unable to tell me HOW to find the trouble, and so they drop off the thread. I suppose I could move the connections along the board, and I'll do that. The module has both 4.7uf and 0.01 uf caps from the power supply to ground. They connect the UNO's A4 and A5 pins to the module. They are individual wires about 15 cm long each. They don't make good contact a lot of times.
The I2C device should have 100nF for the supply voltage. Perhaps you have long wires, say more than 50cm, and they are close to each other, that could be a problem. Perhaps you have a few breakout boards with pull-up resistors on every breakout board, the total pull-up could be below 1k.
The 4k7 is the right value, it should work.
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