Pmod BLE Reference Manual
The Digilent Pmod BLE (Revision A) is a powerful peripheral module meant for use with
any UART enabled development board. This Pmod employs the Roving Networks
RN4870 to create a fully integrated Bluetooth Low Energy interface. This chip features
an onboard Bluetooth stack that makes connecting and communicating with any
Bluetooth 4.0+ device possible through simple UART commands. The RN4870 also
features four built in GATT services: Device Information, Airpatch, BeaconThings, and
UART Transparent data streaming. It also allows up to five custom public services and
up to 4 custom private services, each allowing up to eight custom characteristics. The
PmodBLE is a cheap, versatile, low energy addition to the wireless Pmod library.
Features
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Fully Qualified Bluetooth® Low Energy Module
On-Board Bluetooth 4.2 Low Energy Stack
Certified to FCC, IC, CE, KCC, NCC and SRRC
ASCII Command Interface API
Secure communication AES128 Encryption
Remote Configuration Over The Air
Small PCB size for flexible designs 1.0“ x 0.8” (2.57 cm × 2.03 cm)
12-pin Pmod connector with UART interface
Follows Digilent Pmod Interface Specification Type 3A
Specifications
Parameter
Min
Typical
Max
Units
Power Supply Voltage
1.9
3.3
3.6
V
Baud Rate
2400
115200
921000
bps
Data Rate (Transparent UART)
10
kbps
Parameter
Value
RX Sensitivity
-90
dBm
TX Power
0
dBm
Frequency Band
2.402 - 2.480
GHz
Pinout Table Diagram
Pin
Signal
Description
1
RTS
Ready to Send
2
RXD
Receive Data
Pin
Signal
Description
3
TXD
Transmit Data
4
CTS
Clear to Send
5
GND
Power Supply Ground
6
VCC
Power Supply (3.3V/5V)
7
P1_2
Configurable GPIO
8
RST_N
Reset (Active Low)
9
MODE
App/Test Mode pin
10
P1_6/STATUS
Configurable Connection Status
11
GND
Power Supply Ground
12
VCC
Power Supply (3.3V/5V)
Jumpers
The Pmod BLE has one jumper connected to the MODE pin. When left unshorted, the
PmodBLE will start up in standard application mode. When shorted and power cycled,
the board will go into test mode, which is used to update the firmware on the RN4870.
There is also an unloaded jumper J2 which provides access to 3 configurable pins
P1_3, P1_7, and P2_7.
Physical Dimensions
The pins on the pin header are spaced 100 mil apart. The PCB is 1.011 inches (2.570
cm) long on the sides parallel to the pins on the pin header and 0.8 inches (2.032 cm)
long on the sides perpendicular to the pin header. The PCB on the RN4780 module
extends the length of the PCB approximately .158 in (4.00 mm) and is .355 in (9.00 mm)
wide.
Functional Description
The Pmod BLE uses a 12-pin Pmod port and communicates via UART on the top row of
pins. The bottom row of pins include 2 GPIO pins, a reset pin, and a mode pin that is
used to update the firmware of the BLE module.
The typical application for the Pmod BLE is to replace a wired UART connection
between two Bluetooth capable devices. When paired with an Android, Linux,
Mac OS X, or Windows computer, the Pmod BLE behaves like a serial port similar to
how a USB-UART bridge or RS-232 serial port behaves. The Pmod BLE can be easily
configured from the Bluetooth connected computer by entering a “Command Mode” that
allows settings such as UART baud rate to be programmed into non-volatile
configuration registers.
When used with another Pmod BLE, a wireless UART bridge can be achieved with no
need for software configuration of the Bluetooth link. This is accomplished by entering a
command mode while connected to the PmodBLE through UART. Once in command
mode, the device can connect to any BLE address using the “C,0,<address>”
command. In this way you can communicate wirelessly between two embedded devices
without complicated software like is required with WiFi or 802.15.4 solutions.
Communicate wirelessly with simple serial prints and reads!
WARNING: Hot-plugging (un-plugging or plugging in the device while powered) the
Pmod BLE can possibly wipe the internal memory on the device. Fixing this requires a
UART terminal connection between a PC and the Pmod BLE.
Serial Communication
The Pmod BLE communicates with the host board via the
UART protocol.
By default,
the UART interface uses a baud rate of 115.2 kbps, 8 data bits, no parity, and a single
stop bit. The startup baud rate may be customized to predefined rates or set to a
specific user customized baud rate ranging from 2400 bps to 921 kbps.
By default, the PmodBLE is configured as a transparent UART device. UART data sent
to the PmodBLE will be sent directly to the device it is connected to and vice versa.
Command mode can be entered by sending the module the characters “$$$” to which it
will respond “CMD> ”. When in command mode, the module will respond to a large
number of commands allowing the user to customizing the module for specific
applications. In order to exit command mode, send “—<cr>” (three minus signs in a row
followed by the carriage return character) to which the device will respond “END”.
Remote configuration, or configuration over a Bluetooth connection, is possible using
the command “!,1”. It is important to note that any of the “set” commands available for
the Pmod BLE must be followed by a power cycle to take effect in any design.
GPIO
The reset pin (RST) on J1 is active low. If the RST pin is pulled low, the device will
undergo a hard reset until the RST pin is pulled high. This hard reset performs similarly
to a power cycling of the device.
The P1_6/STATUS pin directly reflects the connection status of the device. STATUS is
driven low by the device when connected and is driven high otherwise. P1_6 can be
reconfigured to several different functions using the SW command (see RN4970 User
Guide).
The P1_2 GPIO pin can be written to by entering command mode and sending the
command “|O,08,0X\r\n” (replace X with 8 to set the pin high, or 0 to set the pin low). It
can also be read from using the command “|I,08”. P1_2 can also be reconfigured to
several different functions using the SW command.
Quick Start
Here is an example of using the PmodBLE to echo data via bluetooth.
1. Disconnect jumper JP1
2. Power on PmodBLE
3. Wait for data to be received, when data is received send it back
while(1){
if(!UART_Buffer_Empty){
ReadUARTData(readBuffer);//Read UART data into a buffer
SendUARTData(readBuffer);//Send that same buffer back
}
4.
5.
6.
7.
Connect to the PmodBLE using a BLE terminal app on your phone
Select a characteristic to read and write data in the BLE terminal
Type something into the terminal and send it
The PmodBLE will echo this data back
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