Author Topic: long range low bitrate library config?  (Read 3392 times)

camdenl

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long range low bitrate library config?
« on: December 19, 2013, 10:01:32 PM »
So I'm hoping to revive previously discussed topics (and finally get an answer this time  :P) and ask if anyone has a stable library config for longer range and lower bitrate.

A

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Re: long range low bitrate library config?
« Reply #1 on: December 20, 2013, 12:20:58 AM »
It looks like the relevant lines in the library are:

    /* 0x03 */ { REG_BITRATEMSB, RF_BITRATEMSB_55555}, //default:4.8 KBPS
    /* 0x04 */ { REG_BITRATELSB, RF_BITRATELSB_55555},
    /* 0x05 */ { REG_FDEVMSB, RF_FDEVMSB_50000}, //default:5khz, (FDEV + BitRate/2 <= 500Khz)
    /* 0x06 */ { REG_FDEVLSB, RF_FDEVLSB_50000},

Felix has defined all sorts of bitrates in https://github.com/LowPowerLab/RFM69/blob/master/RFM69registers.h

He has said that timings and registers are finicky on these radio modules, but have you jumped in and tried some lower bitrates? Based on the datasheet ( http://www.hoperf.com/upload/rf/RFM69HW-V1.3.pdf ) you should be able to go down to 1.2kbps.

camdenl

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Re: long range low bitrate library config?
« Reply #2 on: December 20, 2013, 10:26:22 AM »
I have not changed anything yet, I've seen this posted a few times and was hoping someone had done the experimenting for me  :P


Felix

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Re: long range low bitrate library config?
« Reply #3 on: December 20, 2013, 04:26:11 PM »
Here's a working config for 19200kbps, effectively 2.9x slower than the default 55.5kbps, so it should yield longer range:

    /* 0x03 */ { REG_BITRATEMSB, RF_BITRATEMSB_19200}, //default:4.8 KBPS
    /* 0x04 */ { REG_BITRATELSB, RF_BITRATELSB_19200},
    /* 0x05 */ { REG_FDEVMSB, RF_FDEVMSB_25000}, //default:5khz, (FDEV + BitRate/2 <= 500Khz)
    /* 0x06 */ { REG_FDEVLSB, RF_FDEVLSB_25000},
    /* 0x19 */ { REG_RXBW, RF_RXBW_DCCFREQ_010 | RF_RXBW_MANT_24 | RF_RXBW_EXP_3 },
    /* 0x3d */ { REG_PACKETCONFIG2, RF_PACKET2_RXRESTARTDELAY_NONE | RF_PACKET2_AUTORXRESTART_ON | RF_PACKET2_AES_OFF }, //RXRESTARTDELAY must match transmitter PA ramp-down time (bitrate dependent)

camdenl

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Re: long range low bitrate library config?
« Reply #4 on: March 18, 2014, 04:55:48 PM »
Felix,

Will this also work in high power mode, ie for the RFM69HW?

Felix

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Re: long range low bitrate library config?
« Reply #5 on: March 18, 2014, 05:14:16 PM »
Yes I would think so.

chalupien

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Re: long range low bitrate library config?
« Reply #6 on: March 19, 2014, 01:19:32 PM »
WHen changing the bitrate should the REG_FDEVMSB & REG_FDEVLSB (frequency step) also be changed?


 /* 0x03 */ { REG_BITRATEMSB, RF_BITRATEMSB_19200}, //default:4.8 KBPS
    /* 0x04 */ { REG_BITRATELSB, RF_BITRATELSB_19200},
    /* 0x05 */ { REG_FDEVMSB, RF_FDEVMSB_25000}, //default:5khz, (FDEV + BitRate/2 <= 500Khz)
    /* 0x06 */ { REG_FDEVLSB, RF_FDEVLSB_25000},
    /* 0x19 */ { REG_RXBW, RF_RXBW_DCCFREQ_010 | RF_RXBW_MANT_24 | RF_RXBW_EXP_3 },
    /* 0x3d */ { REG_PACKETCONFIG2, RF_PACKET2_RXRESTARTDELAY_NONE | RF_PACKET2_AUTORXRESTART_ON | RF_PACKET2_AES_OFF }, //RXRESTARTDELAY must match transmitter PA ramp-down time (bitrate dependent)