Addressing Format: Understanding Addressing and Topology

Table of Contents

• Overview
• Decimal, Octal and Binary formats
• Available Addresses
  • Decimal, Octal and Binary
• Displaying Addresses

An overview of addressing in RF24Network

Overview

The nrf24 radio modules typically use a 40-bit address format, requiring 5-bytes of storage space per address, and allowing a wide array of addresses to be utilized. In addition, the radios are limited to direct communication with 6 other nodes while using the Enhanced-Shock-Burst (ESB) functionality of the radios.

The NRF52x modules use a similar format for addressing, but can communicate directly with 8 other nodes while using the Enhanced-Shock-Burst (ESB) functionality of the radios.

RF24Network uses a simple method of data compression to store the addresses using only 2 bytes, in a format designed to represent the network topology in an intuitive way. See the Topology and Overview page for more info regarding topology.

Decimal, Octal and Binary formats

Say we want to designate a logical address to a node, using a tree topology as defined by the manufacturer. In the simplest format, we could assign the first node the address of 1, the second 2, and so on. Since a single node can only connect to 6 other nodes (1 parent and 5 children) subnets need to be created if using more than 6 nodes. In this case, the

• children of node 1 could simply be designated as 11, 21, 31, 41, and 51
• children of node 2 could be designated as 12, 22, 32, 42, and 52

The above example is exactly how RF24Network manages the addresses, but they are represented in Octal format.

Available Addresses

RF24Network supports various configurations, but by default has multicast enabled. This means one additional pipe is taken up on each node for multicasting. The master node will support 5 nodes (01 through 05) and 1 multicast address, while the nodes themselves will support 4 nodes (01n to 04n etc), 1 multicast address and 1 parent pipe. Users can edit RF24Network_config.h and comment out #define RF24NetworkMulticast as well. This allows the master to support 5 children, with nodes supporting 5 children also. See the Topology and Overview page for more info regarding topology.

With the newer NRF52x devices, the master node will support 7 nodes (01 through 07) and 1 multicast address, while the nodes themselves support 6 nodes (01n to 06n etc), 1 multicast address and 1 parent pipe.

Decimal, Octal and Binary

Decimal	Octal	Binary
1	01	00000001
11	013	00001011
9	011	00001001
73	0111	01001001
111	0157	01101111

Since the numbers 0-7 can be represented in exactly three bits, each digit is represented by exactly 3 bits when viewed in octal format. This allows a very simple method of managing addresses via masking and bit shifting.

Displaying Addresses

When using Arduino devices, octal addresses can be printed in the following manner:

uint16_t address = 0111;
Serial.println(address, OCT);

Printf can also be used, if enabled, or if using linux/RPi

uint16_t address = 0111;
printf("0%o\n", address);

See also

• This cplusplus.com tutorial for more information number bases.
• The Topology and Overview page for more information regarding network topology.