LowPowerLab Forum
Hardware support => Moteino => Topic started by: camdenl on December 19, 2013, 10:01:32 PM
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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.
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It looks like the relevant lines in the library (https://github.com/LowPowerLab/RFM69/blob/master/RFM69.cpp) 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.
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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
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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)
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Felix,
Will this also work in high power mode, ie for the RFM69HW?
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Yes I would think so.
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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)