Customer Problem
Find a reliable solution to provide low power long range wireless connectivity to monitor dam pumps and utilities in rural application with differing landscape, foliage and humidity.
Options considered are with the soon to be released Bluetooth Low Energy Long range modules compared to 915MHz radio transceivers.
Option 1 – BT5 Long range Bluetooth Low Energy 2.4GHz transceiver
Advantages:
- 32-bit ARM M4F, 1MB flash, 256kRAM, +8dBm TX, -103dBm RX @ 125kbps
- Low power 1.7-5.5V operation
- Multiprotocol 2.4GHz BT5 transceiver, ANT and proprietary 2.4GHz protocols.
- Interoperability with Android, iOS and other BLE devices.
- Bluetooth 5 long range (500kbs and 125kbs)
- Theoretical line of sight over 2km
- MESH capable
Option 2 – SAMR30 Low Power 769-935MHz single chip long range transceiver.
Advantages:
- Cortex M0+, 256KB Flash / 32KB RAM, +11dBm TX, -110dBm RX
- Ultra Low power 700nA typical with RTC, 1.8-3.6V operation
- Wake from serial communication or GPIO while consuming a mere 500 nA.
- 780 MHz (China), 868 MHz (Europe) and 915 MHz (North America)
- Simple O-QPSK and BPSK modulation schemes.
- More predictable link margin.
- Line of sight 3 Km based on;
- BPSK modulation, 925MHz, 8dBm Tx power, 15dB Fade Margin, 3dB antenna gains, receiver sensitivity -110dB.
- MESH capable
Conclusion
In summary and after careful consideration of both options, Option 2 was selected for the following reasons:
1 – Customer application does not require interoperability and can benefit from the proprietary protocol and basic modulation schemes available with the SAMR30 series.
2 – The Cortex M0 core is a much smaller lightweight MCU capable of waking on interrupt, GPIO or serial input at less than 700nA quiescent.
3 – The 915MHz frequency provides greater penetration than 2.4GHz and therefore is more reliable in congested bushland and higher ambient moisture levels.