humidity sensor

Hi arduinauts,

I just got an humidity sensor module from ebay :

it's a HF3223 module based on the HS1101 chip. (Temperature-Relative-Humidity-Sensor-Module)

And I'd like detailed informations on how to interface it with my new duecimillanove.

I don't know how to 'plug' it (digital/analog?? wich pin to use? etc..) Any help will be appreciated.



actually, it is this one :

thanks for helping me

The auction mentions SPI. That is a form of Serial interfacing like I2C. Other temperature and humidity sensors like from sparkfun and solarbotics use analog inputs like a pot.

There is an SPI library over in the Playground under Interfacing with Hardware. :)

Thanks a lot TLas,

I tought about simply connect it to 2 analog pin (one for T, one for H). What's the point about your SPI library...I don't understand ?

Sorry for this complete newbie question.

Best regards,


Hi TLas,

Like this I mean :

Is it possible or am I completely wrong?

Yes that is a serial type interface, notice the bit shift in the one digital input pin not an analog pin. A typical thermisister uses an analog input pin. The schematic and scheme are a single use routine. The SPI library is reusable code for other SPI devices too. I haven't read a lot about the subject but I think the difference between SPI and I2C is that I2C allows multiple devices on the same pair of wires and each one is polled using an address. That is sort of the way ethernet works. Each packet has a mac address of it's destination.

Hi Mr. Crowley,

I really appreciate your advises and I understand your 2 points. I'm a beginner with the Arduino suite but I already love it. Basically, it will be a way easier to use the digital interface as you suggested. can you elaborate the difference between UART and SPI? can you throw some hints about the wiring and the librairies involved? Do you have a sample code?

My best regards,


Mr. Crowley,

is it the way to go : ???

It seems complicated... Can you simplify things a bit for me?

thank you Antoine

Thanks again Mr. Crowley, I'll read and study about the SPI communication method this week.

Here is the datasheet for the HTF3223:

antoine_b have you had any success?