Jee Labs Talk

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1. mars
   

   I got my JeeNode/JeeLink stuff and hooked the JeeLink into my Windows 7 PC. Drivers where automatically installed, and when I started the Arduino IDE, choose the COM3 port, opened the serial monitor, choose the 57k6 baudrate I was suprised by this (time/date added by me by hitting F5 in notepad):

   -----

       Current configuration:
        A i1 g212 @ 433 MHz 

       13:13 13-5-2010
        ? 150 223 252 43 29 23 255 124 201 1 135 123 56 71 191 254 15 219 127 185 254
        ? 44 189 160 255 124 223 226 255 220 122 23 189 252 247 234 255 246 126 229 253 30

       13:15 13-5-2010
        ? 190 247 239 239 93 246 97 180 181 117 163 239 137 63 109 125 249 215 189 83 47

       13:16 13-5-2010
        ? 63 255 241 252 151 151 92 39 7 247 255 222 87 123 255 255 109 237 207 174 117

       13:19 13-5-2010
        ? 151 126 31 167 127 180 79 243 245 252 191 175 187 63 172 79 133 232 237 75 191

       13:20 13-5-2010
        ? 139 111 255 255 230 185 137 124 255 214 191 255 55 138 254 207 183 255 94 23 247

       13:22 13-5-2010
        ? 187 252 254 77 61 36 125 7 149 71 165 135 242 29 255 115 223 235 222 210 29

       13:23 13-5-2010
        ? 27 76 3 167 0 50 29 110 255 223 127 189 49 123 61 251 199 205 188 247 223

       13:24 13-5-2010
        ? 25 182 253 178 143 234 223 203 231 255 204 227 104 127 254 249 116 247 255 249 183

       13:27 13-5-2010
        ? 189 158 176 255 144 111 231 117 185 121 118 241 227 62 228 135 247 227 121 158 246
        ? 61 183 39 102 243 229 59 127 168 222 126 250 127 147 196 187 239 242 219 218 175

       13:30 13-5-2010
        ? 188 111 59 229 187 223 155 221 251 184 186 95 63 75 151 255 179 223 214 30 206
        ? 21 9 110 250 246 181 174 116 123 83 60 60 92 159 215 157 167 251 247 221 245
        ? 157 253 151 175 247 63 123 255 110 247 191 243 116 207 172 229 127 250 61 215 203

       13:31 13-5-2010
        ? 31 121 135 49 63 223 254 239 127 199 61 247 55 191 63 139 127 79 227 45 191

       13:34 13-5-2010
        ? 167 13 89 180 23 29 43 179 123 221 55 78 127 3 212 249 203 175 205 119 127
        ? 30 109 253 208 31 15 222 239 221 63 57 95 175 253 215 221 189 99 179 158 158

       13:37 13-5-2010
        ? 191 63 250 247 171 255 245 253 127 127 219 247 148 219 211 13 238 222 85 55 115

       13:38 13-5-2010
        ? 181 127 124 126 123 183 150 114 100 223 111 246 249 191 93 158 33 233 73 226 121
        ? 167 23 255 247 204 96 164 93 131 64 233 104 202 218 223 159 0 93 147 254 123

       13:40 13-5-2010
        ? 182 247 219 239 86 247 218 250 75 223 243 94 30 87 191 110 254 255 255 127 168

       13:42 13-5-2010
        ? 45 239 143 127 208 142 115 181 255 45 41 255 79 191 154 250 191 59 89 222 51

   ---- So what am I receiving on the 433Mhz band, FSK coded, and with a pretty consistent 21 bytes message length??

   Posted 13/05/2010 11:45:28

2. jcw
   

   The message length is deceptive - only the first 20 data bytes are printed, so it could be longer - and varying.

   Hard to tell what causes this. Some wireless headphones constantly send on 433 MHz, for example. There are no limits to how much you can send on 433 MHz, so I suspect there is something transmitting 100% of the time - the RFM12B picks up "packets" whenever the two sync bytes match, in your case every few minutes. Since the CRC never matches, the packets will be reported as bad.

   Switching to 868 MHz ought to get rid of all that.

   Posted 13/05/2010 13:07:36

3. mars
   

   I switched to 868 Mhz, but same problem: even more invalid messages are received. Switching to 915 Mhz seems to solve it: no messages any more for at least 15 minutes now!

   I assume that's ok if I set the JeeNode also to that frequency (and of course another node id) or is this an illegal frequency in NL and therefore so 'clean' ?

   Edit/Update: After 30 minutes, 10 messages are received on the 915 Mhz band, so it doesn't seem to matter which frequency I choose: I keep receiving bad messages...

   Posted 13/05/2010 17:30:15

4. jcw
   

   1 msg per 3 min is not unusual. It depends on many things, time of day even. Again: the messages won't pass because the length byte will be incorrect or the CRC check will fail. If you're worried about the minute chance that one gets through, add some known content to your valid packets and check for it.

   Note also that receivers use AGC. So in the absence of a valid signal, they set the receivers more and more sensitive. Try listening on 868 MHz group 1 for example, while periodically sending out packets with another node in group 2. It won't get through, but the presence of real packets should adjust the gain of all the receivers. The result should be that you see less garbage packets come in.

   Another point is that 868 MHz is approx 2x 433 Mhz. So a real nasty xmitter @ 433 could affect both bands (and much less so 915 MHz).

   I'd be more concerned that on 868 MHz you get so much interference that real comms is affected. We disconnected our old Sennheiser wireless headphone, once I found out that it just jams way too many things around here.

   Try tracking the invalid messages over a few days. Maybe it is correlated to your neighbours' gadget habits or something...

   Posted 13/05/2010 18:57:08