User's Manual

LoRa/BLE Modules
Hardware Integration Guide
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Figure 5: Wiring for 2-Wire SWD Programming/Debug Interface connector to SWD Programming/Debug interface on RM1xx module
RM1xx on-board chip antenna characteristics
The RM1xx on-board chip monopole antenna radiated performance depends on the host PCB layout.
RM1xx development board was used for RM1xx development and antenna performance evaluation. To obtain
similar performance follow guidelines in section PCB Layout on Host PCB for RM1xx to allow the on-board
antenna to radiate and reduce proximity effects due to nearby host PCB GND copper or metal covers.
RM1xx on-board antenna part number: ACX: AT5020-E3R0HBANT/LF
HARDWARE INTEGRATION SUGGESTIONS
Circuit
The RM1xx-series module is easy to integrate requiring no external components on the customer’s board apart
from those required by customer for development and in customers end application.
Checklist (for Schematic):
 VCC
External power source within the operating range, rise time and noise/ripple specification of RM1xx.
Add decoupling capacitors for filtering the external source. Power-on reset circuitry within RM1xx series
module incorporates brown-out detector, thus simplifying power supply design. Upon application of
power, the internal power-on reset ensures module starts correctly.
 AIN (ADC) and SIO pin IO voltage levels
RM1xx SIO operating voltage levels are from 0V to VCC. Ensure input voltage levels into SIO do not exceed
VCC also (if VCC source is a battery whose voltage will drop). Ensure ADC pin maximum inpu voltage for
damage is not violated.
 AIN (ADC) impedance and external voltage divider setup
If one wanted to measure with ADC, a voltage higher than 3.6V then one can connect a high impedance
voltage divider to lower the voltage to the ADC input pin. Other methods are to use a voltage buffer or
FET transistor in conjunction with a low resistance voltage divider.
High impedance values of a voltage divider connected to an AIN pin will introduce ADC inaccuracy. Laird
recommends the following solution for setup of a voltage divider when used with the RM1xx ADC:
– Connect a capacitor between AIN and ground (if the voltage divider presents high impedance).
Normally, when ADC is not sampling, the ADC (AIN) impedance is a very high value and can be
considered an open circuit. The moment ADC is sampling, ADC (AIN) impedance is 200k-600k and
JP1
FTSH-105
1 2
3 4
5 6
7 8
9 10
SWDCLK
VCC_IO
nRESET/SWDIO
GND
(RM1xx Pin 22)
(RM1xx Pin 23)