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Arduino microcontroller and nRF24L01+ transceivers
This document describes the implementation of a wireless sensor network using Arduino microcontrollers and nRF24L01+ radio transceivers. It discusses how the nodes in the network receive sensor measurements and forward them to a central node. It provides details on the Arduino Leonardo microcontroller and nRF24L01+ transceiver specifications, including data rates, frequency range, and modulation used. It also describes the RF24 library for communicating between transceivers and proposes a mechanism for packet retransmission with randomized backoff to avoid collisions.
Arduino microcontroller and nRF24L01+ transceivers
- 1. Arduino microcontroller andnRF24L01+ transceivers Pavlos Kallis Supervisor : prof. Leandros Tassiulas University of Thessaly Network implementation testbed laboratory (NITLAB)
- 2. Purpose Deployment of awireless sensor network using arduino microcontrollers and nRF24L01+ transceivers
- 3. Wireless sensor network â—Ź Nodesreceive measurements through sensors â—Ź Nodes forward measurements to a central node
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- 7. NRF24L01+ Transceiver Data Rates:250 kbps, 1 Mbps, 2 Mbps
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- 13. NRF24L01+ TX/RX ● Auto packetassembly ● Auto ACKs and retransmissions – Configurable # of retries – Configurable delay between retries
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- 17. RF24 library â—Ź â—Ź Software forPoint-to-point communication between nRF24L01+ transceivers Abstracts low-level communication between the microcontroller and the transceiver
- 18. RF24 library configuration â—Ź Channel â—Ź Payload size â—Ź Datarate â—Ź ACKs or no â—Ź Retry delay â—Ź Number of retries â—Ź CRC length
- 19. Schematic to connectarduino leonardo with nRF24L01+ transceivers
- 20. RF24 Library examplesetup Pong role 2) Pong role replies with timestamp 1) Ping role sends its timestamp Ping Role 3) Ping role calculates round-trip time
- 21. RF24 Library transmissionmechanism â—Ź When two transmitters send a packet simultaneously
- 22. RF24 Library transmissionmechanism ● When two transmitters send a packet simultaneously – A collision occurs RX TX TX
- 23. RF24 Library transmissionmechanism ● When two transmitters send a packet simultaneously – A collision occurs – Receiver cannot decode the message RX TX TX
- 24. RF24 Library transmissionmechanism ● When two transmitters send a packet simultaneously – A collision occurs – Receiver cannot decode the message – The transmitters will retry in the SAME time slots – Until maximum no. of retries reached
- 25. Proposed mechanism ● If atransmitter fails to transmit a packet(no ack received) – It will wait for a random period, then retransmit
- 26. Proposed mechanism ● If atransmitter fails to transmit a packet(no ack received) – It will wait for a random period, then retransmit – The random period is selected from a contention window, that is doubled every time the TX fails to transmit a packet
- 27. Proposed mechanism ● If atransmitter fails to transmit a packet(no ack received) – It will wait for a random period, then retransmit – The random period is selected from a contention window, that is doubled every time the TX fails to transmit a packet – Until the maximum number of retries is exceeded
- 28. Proposed mechanism :Implementation â—Ź â—Ź Disabled the retransmission mechanism by calling setRetries(0, 0) Built on top of write(buf, len)
- 29. Proposed mechanism :Implementation ● Problem : The function write was poweringDown() the transmitter after a packet transmission – – ● Increased delay to wake ( 1.5 ms) Our random backoff time was much less than that Solution : We disabled the powerDown() function
- 30. RF24Network Library â—Ź Network layersoftware library for nRF24L01+ transceivers â—Ź Built on top of RF24 library â—Ź Handles transmissions in network layer
- 31. RF24Network Library ● Tree topology – Maxno. of children = 5
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