Integration Guide

SMK900 Integration Guide Revision 4
Power Supply and Input Voltages
SMK900 radio modules can operate from an unregulated DC input in the range of 3.3 to 5.5 V with a
maximum ripple of 5% over the temperature range of -40 to 85 °C. Applying AC, reverse DC, or a DC
voltage outside the range given above can cause damage and/or create a fire and safety hazard. Further,
care must be taken so logic inputs applied to the radio stay within the voltage range of 0 to 3.3 V.
Signals applied to the analog inputs must be in the range of 0 to ADC_EXT_REF (Pad/Pin 25) if the
reference is used as such, else the range of 0 to VCC shall be used. Applying a voltage to a logic or
analog input outside of its operating range can damage the SMK900 module.
ESD and Transient Protection
The SMK900 circuit boards are electrostatic discharge (ESD) sensitive. ESD precautions must be
observed when handling and installing these components. Installations must be protected from
electrical transients on the power supply and I/O lines. This is especially important in outdoor
installations, and/or where connections are made to sensors with long leads. Inadequate transient
protection can result in damage and/or create a fire and safety hazard.
In the case where low power consumption is desired, dedicated logic level converters, or equivalent
FET circuitry can be used to achieve such specifications.
Antenna Connector
The antenna connector is a U.FL type male connector which can either be mated to a PCB host board or
directly to an antenna using the appropriate adapter. Impedance of all components from the connector
up to the antenna part has to be 50 Ohms.
Additional I2C Functions
the following I2C commands are available for execution from a custom user VM script(see section 5
for more details):
Name
Type
Description
Master
command byte
stream
Expected slave answer
byte stream
Read
configura
tion
Read
Read in the following order: voltage (1 byte), RF channel (1
byte), I2C address (1 byte), expected reference voltage (2 bytes,
Little-Endian byte ordering). Voltage is the input VCC voltage
of the external sleep controller, using the internal chip FVR
voltage reference. Precision expected of this voltage
measurement is ±0.15 V, and is thus usually sufficient to
evaluate battery pack status if standard alkaline batteries are
used. The raw voltage value sent VRAW is in increments of
0.05V, and is an unsigned 8-bit integer. In other terms, V[Volt] =
VRAW * 0.05. The expected reference voltage REFVOLT is the
actual reference voltage of the internal FVR used for ADC
measurements, which defaults to 2048 mV (value stored in
16-bit as a mV value). In the case where there is a discrepancy
in the voltage assessment of VCC by the external sleep
controller V
ext
and a calibrated measurement in laboratory V
lab
,
then the REFVOLT should be corrected in the following
manner: REFVOLT <= REFVOLT * V
lab
/ V
ext
.
[(ADDR * 2)+1]
[VOLTAGE,
RF channel,
ADDR,
REF voltage LS byte,
REF voltage MS byte]
18