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Semtech SX12xx Radios

The Semtech SX1212, SX1231, SX1231H, SX1233, and SX1282 are radios that can support the DASH7 Mode 2 standard, which is used by OpenTag. At the time of writing (03/2012), OpenTag officially supports the SX1212 and SX1231. Hypothetically, the SX1231H is also supported, because it is just a higher-power version of the SX1231, but it has not been tested.

SX1212 Radio

SX1212 Main Article
The primary advantage of SX1212 transceiver is receiver current consumption in the 3mA to 3.5mA range.

  • This radio transceiver supports 55,555bps rate of Dash7.
  • 200Kbps is not possible with this die. Instead, this rate is supported by SX1231 and other more recent designs. Users who desire superior RF performance should consider SX1231 instead.
  • Tag on this platform should be able to sleep for wake signal at better than 10μA current, due to wake signal recognition capability in under 5ms. Tags should be able to wake every 2.2 seconds to acquire a 2.35-second wake transmitter.

Official Boards That Use SX1212

Board Name/Link STM32 Variant Radio Features
DK7A433 Semtech SX1212 DASH7 dev kit STM32L151CBT6 SX1212 16KB SRAM, 128KB Flash, integrated USB, 2 LED, integrated antenna

SX1231 Radio

SX1231 Main Article
SX1231 radio transceiver is a completely different beast than the SX1212. Compared to the SX1212, the SX1231 has superior RF performance:

  • Supports both 55,555bps and 200Kbps over-the-air bitrates.
  • Transmitter:
    • Much cleaner signal: PLL frequency synthesizer has much lower phase noise and spurs, while achieving lock time of 80 microseconds typical.
    • Modulation shaping. Complies with 216KHz channel bandwidth requirement of Mode-2.
    • +13dBm standard power output, +17dBm optional with external RF switch.
  • Receiver:
    • much wider dynamic range (range of signal amplitude into receiver).
    • RSSI dynamic range of 115dB.
    • superior handling of strong adjacent signals, also known as blocking immunity.
  • lower external component count: PLL is implemented entirely on silicon, no external tank circuits or loop filters.
  • 100nA leakage current in sleep mode, with worst case wake-up time of half millisecond.
  • frequency range coverage: 290 to 1020MHz.
  • packet engine optional feature of AES 128bit fixed key cipher. (not used with Dash7)
opentag/radios/sx12xx.txt · Last modified: 2012/06/29 14:35 by jpnorair