The hard RAK831 cafe part 2

(Gry Kyo) #103

It seemed to be just fine until I read your post and checked the dashboard…

12.03.18 00:28:33 (+0000) Restarting application '…'
12.03.18 00:28:36 (+0000) Application exited ‘…’

I won’t get to look at this for a day or so but it looks like the gateway is a bit sick! Keeps restarting the application and crashing/halting/exiting after 3 seconds. I can’t seem to start a SSH session either to see if the Pi is even running OK!

SSH reconnecting…
Spawning shell…
rpc error: code = 2 desc = invalid character ‘e’ looking for beginning of value
Error response from daemon: Container 5a…2 is restarting, wait until the container is running
SSH session disconnected

(Coeus) #104

Anyone here looking to build a RAK831 totally for grids - I am planning to make one with 3G cellular connection, a battery, power management circuit and a solar panel.
Possibly using one of these?
USB / DC / Solar Lithium Ion/Polymer charger

(Tim Everitt) #105

Hi @coeus, I read your question to be “… totally OFF grid …”. I work with small off-grid systems. A TTN gateway with cellular backhaul will consume quite a lot of power, probably 4-5 watts. This picture shows an RPi + iC880a gateway being calibrated for off-grid use with a 24VDC solar+battery system.

This system is consuming 24V x 0.15A = 3.6 watts, and that is before the cellular backhaul is added.

I strongly suggest that you build your gateway and backhaul system and check it using a good DC lab power-supply in order to understand the power consumption. Then do the sums to calculate how much solar power and battery capacity are needed for your solar availability, seasonality, gateway availability, etc.

I’m at 57deg North with about 6hrs of low sun in the winter and frequent periods of bad weather and run my systems with a 4x margin to avoid over-stressing the batteries or me. That ends up at a 30W solar panel and 100Ah of battery at 12V or 50Ah at 24V. Big and expensive! Reliable!


I need to put the RAK831 in a enclosure and need to remove the SMA connector and I’ve done as follow but not my favorite and easier way to do.

But I see there are 2 diversity interface iPEX connectors on board, anyone knows how to use it (I know in this case that I’ll need 2 antennas, one to receive and one 2 send). Any example configuration of lora gateway json.conf (it it’s in there) to use these 2 instead of the SMA one?

An I think it’s possible we’ve got the smallest outdoor full GW ever :wink:

And with big @BoRRoZ favorite OLED for fun

(Ebreyit) #107

This should help


not so easy, need to open, and switch position of 2 x 0603 capacitor. Risky :wink:
I will keep to remove the SMA connector and put a cable adapter like on picture

(Ebreyit) #109

So what are you going to output to the display. Basic console or something more graphical…?

(Gry Kyo) #110

So being well out of my depth I reinstalled the application which started without a problem. Not entirely sure why the packet forwarder stopped or wouldn’t restart and I haven’t physically examined the installation (it’s up on the roof!)

“gw_id”: “gk_gateway_1”,
“payload”: “QOQjASaAMAAB7vhaV2vxPiO7gGjI”,
“f_cnt”: 48,
“lora”: {
“spreading_factor”: 9,
“bandwidth”: 125,
“air_time”: 185344000
“coding_rate”: “4/5”,
“timestamp”: “2018-03-13T13:48:39.865Z”,
“rssi”: -80,
“snr”: 6,
“dev_addr”: “260123E4”,
“frequency”: 867500000

The first Heltec I pulled out of the parts bin with an antenna plugged in seems to have some code running. To answer your question @BoRRoZ, it seems to have survived the snow but the jury is still out regarding the packet forwarder…


I’ve provided some figures and tips here, if it might be of interest to you.

(88bit) #112

Hi I just deployed a RAK 831 Gateway in the AU915, the installation was straight forward however I’m encountering instability and I’m thinking this is maybe hardware related. I would like to know what the expected signal strength and SNR should be? At a distance of 4m (16 foot) I’m getting -55,25 when running at+signal.
I would have expected much better results given the distance between them. I have now tested with two nodes and the results a similar. All packets are received on SF12 at this distance I would expected SF7 or 8.
At one point I moved the end node directly next to the gateway and had some packets arriving at SF 8.

I some how starting to think that there is something not right with my radio, I tried a couple of different antennas, too. With the same result.

Dose anyone knows of a way to observe the packets coming into the radio of the *831 gateway?

I’m in 915 AU band.


I can see from the missing antenna trace that the RAK831 just hardly survived the (RP-)RMA connector removal. :confused:

Earlier versions had the RP-SMA connector soldered on only one side. That made it much easier to remove than when soldered on both sides.

In case you will have to do it again:
When the RP-SMA is soldered on both sides: first try to remove some of the solder on the bottom side with solder wick and then while the solder is still fluid remove/break off the two grounding solder pins with a small cutting pliers.
This will make it a little easier to remove the connector, but still a nasty job that requires good soldering skills and proper tools.

I see that you use Chinese leaded solder. I think that you will appreciate something like Stannol Kristall 505 in 0.7mm much more (the 0.7mm is also available in 100g package but not listed on the site). It flows much better than several Chinese types (both 63/37 and 60/40) that I have tried (and thrown away).

Time for some bigger case maybe? In combination with an extension/converter cable like this SMA to angle RP-SMA RG316 cable?

(LoRaTracker) #114

RSSI looks about right.
SNR seems to max out at about +10 for me.

I would not rely on tests at such short distances myself.

You could try and ask Rakwireless, they might have a beter idea of what to expect.

(Gry Kyo) #115

Below is from a LoRa32u4 II node placed about 5m almost directly below a 3dbi antenna on the roof of our house, also a RAK831 but on EU868
Settling on sf12 would suggest something is not right with the RF (my limited experience). Everything OK with antenna on the node and gateway?

“gw_id”: “gk_gateway_1”,
“lora”: {
“spreading_factor”: 7,
“bandwidth”: 125,
“air_time”: 51456000
“coding_rate”: “4/5”,
“timestamp”: “2018-03-15T15:18:45.129Z”,
“rssi”: -69,
“snr”: 10.5,


It was soldered on one side, but my fault, wanted to do it too quickly, but never mind this one has fried ;-(

For sure, next DK or mouser order, I’ll take some, thanks

(LoRaTracker) #117

Cant possibly comment, given that its through a building and the node is directly under the antenna where there could (or could not) be a distinct null.

Trying to rely on measurements at such short range, in and around buildings, is a waste of time really.

(LoRaTracker) #118

Although regardless of whether the gear is OK or bad, an RSSI of -69 and SNR +10, is still a strong signal for SF7.

(Gry Kyo) #119

My thoughts too. It is way less than ideal placement of the two antennas but by comparison to a system with lower RSSI and which is selecting a high sf? Here the LoRa seems robust but 88’s?

(LoRaTracker) #120

I do not understand what you mean here.

88s are pairs of fat ladies in bingo I thought.