Datasheet
11
EEH210
v1.0 / Modification rights reserved
RH=-6+125∙
D
RH
2
16
In the example given in Figure 9 and Figure 10 the relative humidity results to be 42.5 % RH.
RH=-6+125∙
25424
65536
=42.492≈42.5
The physical value RH given above corresponds to the relative humidity above liquid water according to World
Meteorological Organization (WMO). For relative humidity above ice RHi the values need to be transformed from relative
humidity above water RHw at temperature t.
The equation is given in the following formular:
RH
i = RHW . exp
β
W . t
λ
W + t
( )
/ exp
β
i . t
λ
i + t
( )
Units are % RH for relative humidity and °C for temperature. The corresponding coefficients are defined as follows:
βw=17.62,λw=243.12°C,βi=22.46,λi=272.62°C.
Temperature Conversion
The temperature T is calculated by inserting temperature data output D
T into the following formula (result in °C), no
matter which resolution is chosen:
T=-46.85+175.72∙
D
T
2
16
7. communication by sPi bus interFace with sensor
The EEH210 SPI is a slave bus that can operate in SPI modes. The SPI allows to write and read the registers of the
device. The serial interface consists of 3 wires: CSB, SPC, SDIO
CSB is the serial port enable and is controlled by the SPI master. It goes low at the start of the transmission and goes
back high at the end. SPC is the serial port clock and it is controlled by the SPI master. It is stopped high when CSB is
high (no transmission). SDIO is the serial port data input and output. This line is driven at the falling edge of SPC and
should be captured at the rising edge of SPC
Both the read register and write register commands are completed in 16 clock pulses or in multiples of in case of multiple
read/write bytes. Bit duration is the time between two falling edges of SPC. The first bit (bit0) start at the first falling edge
of SPC after the falling edge of CSB while the last bit (bit15,bit23, …) starts at the last falling edge of SPC just before the
rising edge of CSB.
7.1. sPi write
Figure 15: Multiple byte SPI write protocol (2-byte example)