Data Sheet

RM1xx LoRa/BLE Modules
Datasheet
https://connectivity.lairdtech.com/wireless-
modules/lorawan-solutions
26
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previous level for an adequate time period while sampling, minimizing the effect of the high resistance
value of the external voltage divider. The capacitor should be big enough to hold voltage up for the
required time period, i.e. 20 us for 8 bit sampling or 68 us for 10 bit sampling. If you use a FET
transistor to open the current flow through the circuit momentarily before sampling, allow enough time
for the capacitor to fully charge before sampling. During the sampling period, multiple samples are
made and the ADC output value is the mean value from the sample pool. The sample pool is created
during 20 us period for 8 bit sampling, 36 us period for 9 bit sampling, and 68 bit period for 10 bit
sampling.
 Two-Wire SWD Programming/Debug Interface (JTAG)
Add 2-Wire SWD Programming/Debug Interface as detailed in section 2-Wire SWD Programming/Debug Interface.
Note: Required if upgrading between central and peripheral firmware capability will be necessary during
production.
 UART
The UART is required for loading customer smartBASIC application and firmware. Add connector to allow UART to be
interfaced to PC (via UART –RS232 or UART- USB).
Note: Not capable of upgrading between central and peripheral firmware via UART.
 UART_RX and UART_CTS
SIO_22 (alternative function UART_RX) is an input, set with internal weak pull-up (in FW). The pull-up prevents the
module from going into deep sleep when UART_RX line is idling.
SIO_24 (alternative function UART_CTS) is an input, set with internal weak pull-down (in FW). This pull-down ensures
the default state of the UART_CTS will be asserted which means can send data out of the UART_TX line. In the case
when UART_CTS is not connected (which we do not recommend).
 nAutoRUN pin and operating mode selection
nAutoRUN pin needs to be externally held high or low to select between the two RM1xx operating modes at power-up:
– Self-contained Run mode (nAutoRUN pin held at 0V).
– Interactive/development mode (nAutoRUN pin held at VCC).
 Make provision to allow operation in the required mode. Add jumper to allow nAutoRUN pin to be held high or low
(via 10K resistor) OR driven by host GPIO.
 I2C
It is essential to remember that pull-up resistors on both I2C_SCL and I2C_SDA lines are not provided in the RM1xx
module and MUST be provided external to the module as per I2C standard.
 SPI
Implement SPI chip select using any unused SIO pin within your smartBASIC application script then SPI_CS is controlled
from smartBASIC application allowing multi-dropping.
 SIO pin direction
RM1xx modules shipped from production with smart
BASIC runtime engine FW, all SIO pins (with “default function” of
“DIO”) are mostly digital inputs (see Pin Definitions Table 2). Use your smart
BASIC application script to change the
direction of any SIO pin that is required to be an output in your design. Also these SIO pins that are inputs have by
default (in FW) an internal pull-up or pull-down resistor-enabled (see Pin Definitions Table 2). This was done to avoid
floating inputs (which can also cause current consumption in low power modes (e.g. Standby Doze) to drift with time.
In any case customer can disable the PULL-UP through their smart
BASIC application.
 SIO_28 pin and Over the Air smartBASIC application download feature
SIO_28 is an input, set with internal pull-down (in FW). Refer to latest FW release documentation on how SIO_28 is
used for Over the Air smartBASIC application download feature. SIO_28 pin has to be pulled high externally to enable
the feature. Decide if this feature is required in production. When SIO_28 is high, ensure SIO_25 (nAutoRun) is NOT
high at same time, otherwise you cannot load the smartBASIC application script.