Hello all,
I have my nano's all set up and receiving temp/humidity and reporting back to my Raspberry PI over 433mhz so thanks for the help with that. I'm now going to get some bmp180's. I do not think these are the official because they have 5 pins. I'm assuming the VCC is not one I care about? 3.3v to 3.3v, GND to ground SDA to A4, SCL to A5?
I do not think these are the official because they have 5 pins.
I have no idea what that means... not official according to whom? How many pins do you want it to have?- adafruit's have 5 as well.
Real question should be, does yours have the 5V to 3V3 I2C logic conversion on board, seeing as the Nano is a 5V device.
I was attempting to avoid the "Chinese knockoff" comments that I've seen on other forums. If that is not necessary here that is awesome.
My nano has a 3.3v pin which does produce 3.3v. It also has a 5v pin that I use for other sensors such as the 433mhz transmitter/receiver.
For sensor breakout boards and simple shit like that, we all use el cheapo chinese boards - there aren't any sort of official boards for them.
sdsheeks:
I was attempting to avoid the "Chinese knockoff" comments that I've seen on other forums.
All the breakout boards are cheap chinese crap - there aren't official versions (well, I think there are for some parts - but they're targeted at industrial users, not hobbyists). For arduino boards with mysterious problems, it is worth noting whether it's a clone, since defective clones are not unheard of.
You can run it at 3V3 or5V, or at least that's what it looks like; the adafruit ones work that way.
But if you use a 5V board like a Nano, the SDA and SCL are at 5V, and that's got nothing to do with how you power your BMP. The adafruit BMP modules take the SDA and SCL down to 3V3, and that's why I asked that you if your modules do that.....
Save yourself a shitload of trouble and get an adafruit one.
That sensor runs perfectly OK without voltage-adjustment to CLK and SDA
knut_ny:
That sensor runs perfectly OK without voltage-adjustment to CLK and SDA
I'll take your word for it, but adafruit says here:
a i2c level shifter circuit is included so you can use this sensor safely with 5V logic
Yepp. Datasheet says nothing. I started out here: SparkFun Barometric Pressure Sensor Breakout - BMP180 - SEN-11824 - SparkFun Electronics
The two transistors (actually mosfets) and four 10K resistors on the Adafruit board are what build the level shifter. The picture sdsheeks has quite clearly has no level shifting -- just two pullup resistors for the I2C lines and a couple caps for either the 3v3 regulator or BMP180 itself.
When you're buying that "cheap crap" if those fets/resistors aren't present then sometimes you'll see a six-pin IC on the board performing the level shifting. If you see neither then you'll need to add your own level shifter -- but again you can find inexpensive versions on eBay.
Why add cost with the the transistors when they are not needed at all? The main chip is the same and is is surely 5V tolerant
They may have simply left the maximum voltage out of the data sheet. Saying nothing doesn't mean it's 5V tolerant any more than it means it's 100V tolerant. It says nothing.
VDDIO is stated as 1.62V to 3.6V. Under maximum ratings it states 4.25V ("all pins"). I see nothing to suggest that it is 5V tolerant.
Maximum supply voltage at "all pins" probably means both Vdd and Vddio, not the interface pins. On their next generation chip, the 280, they are more specific in the data sheet. The maximum for Vdd and Vddio is stated to be 4.25V and for all interface pins it is Vddio+0.3V. So the BMP280 is not 5V tolerant, for whatever that's worth.
I'm using bmp180 with Nano without level shfting. Runs perfectly
mazur888:
I'm using bmp180 with Nano without level shfting. Runs perfectly
So you're driving SCL and SDA with 5V? Interesting. I wonder if that would work with the BMP183 or '280.
yes 5v.
what is the difference between bmp180 and bmp183?
The 183 is the same as a 180 but with an SPI interface instead of I2C.
It's curious that all of these BMP180 shields take the trouble to level shift the interface signals from 5V to 3.3 if it works just fine all the time at 5V.
I take that back. I looked and immediately found a counter-example at Sparkfun. They state that the I/O lines are 5V tolerant without any level shifting. So I wonder why Adafruit bothered to level shift SCL and SDA?