RNode User Manual Thank you very much for buying this product! If you have any questions, suggestions, criticisms or good ideas, I’d love to hear from you! This guide provides a few pointers on getting started with RNode, how to connect to the board, and how configure it.

Device Overview Please have a look at the following chart and familiarise yourself with the different ports, connectors and indicators on your RNode.

Revision 3 - December 2019

Native port number Arduino digital I/O Arduino analog input Additional function

External ResetUART0 RX D7 PD0UART0 TX D8 PD1UART1 RX D10 PD2UART1 TX D11 PD3

GND5V

USB Connector(Mini-B)

SMA Antenna Connector

Multi-purpose LEDs

USB activity LEDs

PWM D14 PD6PWM D15 PD7A0 D24 PA0A1 D25 PA1A2 D26 PA2A3 D27 PA3

PC0 D16 SCLPC1 D17 SDAPC2 D18 TCKPC3 D19 TMSPC4 D20 TDOPC5 D21 TDIAREFPA7 D31 A7

Cautions • Never operate the device without a connected antenna!

Doing so can damage the radio.

• Always ensure a regulated 5V DC supply of correct polarity is used to power the device. Supplying the device with incorrect voltage or polarity will damage the device.

• Always observe your local laws and regulations regarding RF emissions. This device is capable of operating in a wide range of frequency bands and emission modes, some of which may be illegal in your jurisdiction. It is your responsibility to ensure you are operating this device in a lawful way.

Specifications • High-quality LoRa module with genuine Semtech SX1276 chip• Powered by an ATmega1284p MCU clocked at 16 MHz• 128 kilobytes of flash• 16 kilobytes of RAM• Large payloads with a packet MTU of 500 bytes• Max 17 dBm continuous TX output in the 820-1020 MHz band• Max 14 dBm continuous TX output in the 410-525 MHz band• Sensitivity down to -139 dBm• Data rates ranging from 20 bps to 21.88 kbps• Mini-USB connector• SMA antenna connector• Fully programmable• Arduino compatible• Open source firmware and config util• 17 multi-purpose IO ports available• Operating temperature range: -20°C to 60°C (in non-condensing humidity)• 23.3 mA idle power consumption

Connecting RNode to Host Equipment RNode can be connected to any host supporting USB or serial UART connections. The board uses an FTDI USB-to-serial converter, so drivers should already be included in most operating systems. You can use either the USB port, or connect directly to the UART0 RX and UART0 TX ports.

The default firmware uses 115200 baud, 8N1. No UART flow control is used. RTS line is connected to External Reset. Toggling RTS will reset the board.

If you wish to prevent the USB host from being able to reset the board, connect an 80Ω resistor between the pins 5V and External Reset.

Operating Modes RNode can operate in two modes, host-controlled (default) and TNC mode:

• When RNode is in host-controlled mode, it will stay in standby when powered on, until the host specifies frequency, bandwidth, transmit power and other required parameters. In host-controlled mode, promiscuous mode can be activated to sniff any LoRa frames.

• When RNode is in TNC mode, it will configure itself on power-up and enable the radio immediately. This mode can be enabled by using the configuration utility.

Configuring RNode The device is useable out of the box, but can be further configured to your needs by using the RNode Configuration Utility. Please visit the RNode page at https://unsigned.io/rnode for the latest version of the config utility.

Multi-purpose LEDs RNode is equipped with two multi-purpose LEDs close to the antenna port. The LEDs are used to signify a variety of device states and events.

Pattern Description

After powering the device:Blue LED is pulsing slowly

Device is in standby and all health checks and device verification succeeded.

After powering the device:Orange LED is pulsing slowly

Device verification failed, and operation was halted. Possible radio or EEPROM damage.

When radio is on:Blue LED is on

Device is receiving data, or a data carrier was detected on the channel

When radio is on:Orange LED is on

Device is transmitting data

Blue and orange LEDs alternatingly blinks for 3 seconds

Hardware error. Possibly invalid radio parameters were supplied.

Blue and orange LEDs alternatingly blinks for more than 3 seconds

EEPROM is about to be formatted. Power down device within 7 seconds to cancel.

Blue LED emits 3 short blinks Radio powered on and ready

Orange LED emits 3 short blinks Warning indicator. Check error codes sent.

Updating the Firmware You can easily update the device firmware to the latest version by using the RNode Config Utility. Alternatively, you can manually download specific firmware versions from https://github.com/markqvist/RNode_Firmware and flash it manually with avrdude or similar programs.

Programming The easiest way to program RNode is probably from within the Arduino IDE. Even the entire default RNode firmware can be edited and compiled directly from the Arduino environment. For adding RNode to your Arduino IDE, please see https://unsigned.io/board-support-in-arduino-ide/. It is also possible to work with any other toolchain that supports the ATmega1284p that powers RNode, like avr-gcc or similar.

If you want to make your own firmware for RNode, it can be a good idea to use the default firmware as a starting point, since a lot of the setup required to use RNode, such as initialising the LoRa transceiver, is already done for you. The source code for the firmware is available under an MIT license, and can be found here: https://github.com/markqvist/RNode_Firmware.

See the pinout in the beginning of this manual for Arduino pin mappings.

A Few Notes on the EEPROM As a completely open device, RNode does not block you from modifying the EEPROM contents, which specifies things like radio parameters, serial number, manufacture date and similar. But please be aware that doing so might render the device inoperable or burn out the radio.

Before making any modifications, please make sure to create a backup of the EEPROM. RNode includes a cryptographic signature of the EEPROM contents, which validates all the information stored within it. You will not be able to re-create a valid signature if you erase it! Without this signature, the board will still function, but warranty will be void.

If you upload your own programs or alternative firmwares to RNode, you should make sure that they don’t write to the last 200 bytes of EEPROM. You can back up your EEPROM with the config utility.

Interfacing with RNode You can interface directly with the device using the protocol specified later in this manual, or to get started easily, use one of the available libraries. To download libraries and examples, please have a look at: https://github.com/markqvist/RNode_Firmware/tree/master/Libraries.

USB and Serial Protocol Communications to and from the device uses KISS framing with a custom command set. RNode also does not use HDLC ports in the command byte, and as such uses the full 8 bits of the command byte is available for the actual command. Please see table below for supported commands.

Command Byte Description

Data frame 0x00 A data frame to or from the device

Frequency 0x01 Sets or queries the frequency

Bandwidth 0x02 Sets or queries the bandwidth

TX Power 0x03 Sets or queries the TX power

Spreading Factor 0x04 Sets or queries the spreading factor

Coding Rate 0x05 Sets or queries the coding rate

Radio State 0x06 Sets or queries radio state

Radio Lock 0x07 Sets or queries the radio lock

Device Detect 0x08 Probe command for device detection

Promiscuous 0x0E Sets or queries promiscuous mode

Ready 0x0F Flow control command indicating ready for TX

RX Stats 0x21 Queries received bytes

TX Stats 0x22 Queries transmitted bytes

Last RSSI 0x23 Indicates RSSI of last packet received

Blink 0x30 Blinks LEDs

Random 0x40 Queries for a random number

Firmware Version 0x50 Queries for installed firmware version

ROM Read 0x51 Read EEPROM byte

ROM Write 0x52 Write EEPROM byte

TNC Mode 0x53 Enables TNC mode

Normal Mode 0x54 Enables host-controlled mode

ROM Erase 0x59 Completely erases EEPROM

Error 0x90 Indicates an error

Error Codes If an error occurs on the device, it will be signalled to the host using the error command, which will include an error code as command payload. As an example, if the radio could not be initialised, the device will send 0xc09001c0 to the host. The error codes are defined as follows.

Flow Control and Packet Buffer When sending data frames for transmission to the device, RNode employs a simple mechanism of flow control to ensure no packets are dropped due to congestion. When a data frame is is received from the host, the device will put the frame into a queue. By default, the queue can hold up to 24 frames (12 kilobytes of data). If the channel is free, the frame will be transmitted immediately. If there is already activity on the channel, the device will wait until the channel is free, and then send all frames in it’s queue. RNode can receive and queue frames from the host while it is waiting for the channel to become free.

Every time a frame is received from the host, RNode will send a Ready command back to the host (0xc00F01c0), if it is ready for more data. If the queue is full, a Ready command will not be sent. As soon as more space is available in the queue, a Ready command will be sent to the host. If the host sends a data frame when the queue is full, the frame will be dropped, and RNode will send an Error - Queue Full command to the host (0xc09004c0).

Receiving Packets and RSSI When the device is powered up and configured by a host, or operating in TNC mode, it will be listening for packets on the specified frequency. Once a packet has been demodulated, it will be sent as a data frame to the host.

Just before sending the data frame, the device will signal the average RSSI of the packet by sending an RSSI command. Subtract 157 from the received command payload to obtain the RSSI in dBm. As an example, let us assume the command 0xC0233FC0 is received from the device. The command payload is 3F, which is equal to 63. We obtain the RSSI by subtracting the offset: 63 - 157 = -94dBm.

Command Byte Description

Radio Init 0x01 Radio module could not be started

Transmission Failure 0x02 Transmission failed due to a hardware error

EEPROM Locked 0x03 EEPROM write failed due to EEPROM lock

Queue Full 0x04 Data frame dropped because the queue is full

Packet Format and MTU RNode allows large packets with a max payload of 500 bytes. Standard LoRa packets can only carry a payload of 255 bytes, so RNode achieves the larger MTU by directly stringing together two standard LoRa packets.

At the physical layer, a one-byte header is employed, which includes a random sequence number in the most-significant 4 bits, and a split packet flag in the least significant bit. Bits 3, 2 and 1 are reserved for future uses.

This physical layer format is transparent to the host, and 500 byte packets are sent and delivered in exactly the same way as a small packet would.

If you do not need large packet support, but want compatibility with standard LoRa networks, this feature can be turned off, see the next section.

Promiscuous Mode RNode can be put into promiscuous mode to perform packet capture and packet injection on standard LoRa networks. In promiscuous mode, all demodulated LoRa frames will be dumped raw to the host. Raw LoRa frames can also be injected by sending data frames to the device. Standard 255 byte LoRa MTU applies in promiscuous mode.

RNode will demodulate and dump packets with any LoRa coding rate, no matter what coding rate the device itself has been configured to use.

For a ready-to-use LoRa packet sniffer program, have a look at LoRaMon here: https://github.com/markqvist/LoRaMon.

Getting Help If you have any questions regarding RNode, please do not hesitate to send me an email at mark@unsigned.io. You can also register for the forums at unsigned.io where other users might offer pointers and advice.

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