BIG ESP32 / SX127x topic part 1

(Mirtcho) #166

I have experienced similar problem with my ESP32 lora board. See post #122 in this topic. It seems that antenna matching circuit is really bad.
Receive levels with my boards are 10dB lower than other modules that I have


I have done some simple tests and compared Heltec Wifi LoRa 32 with Arduino Pro Mini + RFM95W module (which has SMA connector on the PCB) as nodes (distance 2+m from the gateway). Using the same 868MHz quarter wavelength whip antenna (mounted upright on a metal plate and connected with 15cm cable):
RSSI of the Heltec Wifi LoRa 32 was between -21 and -27dB and about -23dB on average which is 4 to 5dB worse/less than the other module.

Part of this difference (probably several dB) can be explained by losses in the 10cm IPX to SMA converter cable which is needed for the Wifi LoRa 32 but not for the other module.


Just received this rather peculiar device today. So did someone managed to get it running on a Pycom LoPy fork?

(Petriska) #169

May be you can change it like here

(Franc Kralj) #172

I also find that the antenna is poor. I directly connected the antenna 1/4 Lamba and it’s not even better. RSSI -120. It may be that the chip sx1276 has been damaged.


With the small whip antenna included with Heltec Wifi LoRa 32 868MHz (the white board with poor helical Wifi antenna) I get LoRa RSSI of -45 (way better than your -120) reported by the gateway in below situation.
So it could be a problem with your module (or antenna).

Situation: RAK831 based gateway on second floor next to a window.
Heltec Wifi LoRa 32 node on first floor (beneath gateway). Distance 2.75m from Window. Shortest path between node and gateway is 3.85m with a concrete floor between first and second floor.

Node antenna held upright using a soldering stand like:

soldering stand

FYI: The inside of the small whip antenna that was included with the Heltec module is a helical antenna that looks similar to antenna used for GSM. In the same setup I also tested with a (longer) ¼λ antenna but the difference in RSSI between the two antennas was only a few dB. It did not make a big difference in this setup / these conditions.

(Ggeorgiou007) #174


I managed to test (point to point) two of these NODES

  • ESP32+ SX1276 (433MHz) + OLED from HELTEC

  • Yes the antenna design is stupid!

However i managed to GET 8.3 Km RANGE! (packet received using the "TEST " that comes in the EXAMPLES

I am confident that it was NOT a very clear LOS (line of sight) as we can see from google maps - and this was while driving in the highway! Pretty amazing for such a device (El cheapo! device!)

I am sure that i can easily get 20Km…!

8km NON LOS lora test -117 DB|689x481

(Ggeorgiou007) #175

That was at -117 db

Also i dont get anything lower than -120db (its supposed to go down to -140) - however this might have to do with the Arduino software or the board design…


I was wondering if this tutorial that was written for the LoPy also works on the ESP32+sx1276 boards.


good catch, same hardware, should works just according pin mapping on LMIC side. I’ve got 2 of these devices, worth trying :wink:

(Deux Vis) #178

Probably. When I last - successfully - tested one of those device I used LMIC and the arduino IDE.

We should make a version of that story specifically for the Wifi Lora Kit32 then, using the display instead of only the serial terminal.

(Hutje) #179

When I try the LMiC with the Heltec 32 Lora, but I got stuck at EV_JOINING…
Am I doing anything wrong?
The nearest gateway is 300 meters away.
Is there a way to measure the strength of this signal?

ets Jun  8 2016 00:22:57

configsip: 0, SPIWP:0xee
mode:DIO, clock div:1
entry 0x40078a9c

Packet queued
104320: EV_JOINING

Nearest gateway from an agricultural school in the Netherlands

(Biohazard) #181

I received the LoRa1276 modules from NiceRF.
Used on the esp32 core dev board, I’m getting 1.76 mA in deep sleep mode when I was getting 10 mA with vanilla Heltec board.

Still not in the uA range but it’s 5 times less power hungry.

My two cents.


“…We should make a version of that story specifically for the Wifi Lora Kit32 then, using the display instead of only the serial terminal…” - Take a look at post 75 in this thread :slight_smile:

(Dcotelo) #183

Hi @nicbkw
Thanks for the code on your previous post, i’m using this gateway as single channel gateway

but i’m getting stuck at EV_join_failed, i made all the changes on config.h to work on 915 Mhz
is there any chance you have the full code somewhere or any debug i might be missing?

Thanks in advance!

(Richjdavies) #184

CurlyWurly THANKS SO MUCH POST 123 - I just spent my Friday night going through this thread and am now the happy owner of a Heltec TX LMIC sender :smiley:
Just one comment - as its a little confusing with other people talking MSB/LSB for the DevEUI’s - that all the KEYs in your code are in MSB!

For any newbees like me - you can get these all ready to paste from console.
DEVADDR/Device Address just copy the hex and add after the 0x in the code
NWKSKEY and APPSKEY click the eye (show code) then the <> (C-style), click the copy button and then use that to paste into the code (do not press the ⇆ button - check that your showing MSB before copying!)

Anyone know what we need to get this same code in OTAA?

Single Channel Gateway part 2
(Irrlicht) #185

I’m new at TTN, only little experience.
@CurlyWurly: “Post 123” is working, thanks.

Does anybody could provide me full example code for the heltec-board with dht11-Sensor for TTN or a suitable link?

(Andreas) #186

Had success with the Heltec (White, “Spring” WiFi Antenna). I had to add
#define CFG_eu868 1
#define CFG_sx1276_radio 1
to make OTAA work.

Regarding the LED hardware - what is the best way / simplest / reversible to basically “shut down” the charger circuit when it is not used (hopefully shutting down the agitated blinking LED)?

Regarding LiPo operations: has anybody tried this yet? How long does it run?

I assume when using deep sleep we would have to somehow save the OTAA state in the ESPs clock memory so it survives the sleep cycle?


(Verkehrsrot) #187

Thanks for the cooking receipt. Works!

(Verkehrsrot) #188

Tried to activate the sensor node mode in the code by defining #define GATEWAYNODE 1 in ESP-sc-gway.h

This runs on an error when compiling _sensor.ino in this line:

int buff_index = buildPacket(tmst, buff_up, message, mlength, true);

could not convert ‘(uint8_t*)(& message)’ from ‘uint8_t* {aka unsigned char*}’ to ‘LoraUp’