LoRa modules (AI Thinker Ra-01, SX1278)

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RogerClark
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LoRa modules (AI Thinker Ra-01, SX1278)

Post by RogerClark » Sun Nov 12, 2017 7:24 pm

I received some LoRa wireless data modules in the post during the week and finally had time to wire them to a BluePill and a Maple mini

The AI Thinker Ra-01 module uses the SX1278, so is limited to 2 frequency bands, of which only the 433Mhz one can be used without a license.

I did some basic testing using a LoRa library written by Sandeep Mistry ( github.com/sandeepmistry), and they seem to work fine and give much better range then previous generations of wireless data modules.
I can easily get several hundred metres range outdoors in a built up area, when when the antenna is in a terrible location.

I paid $13.6 USD for 4 modules from AliExpress, which seems to be an average price for this sort of module.
(I also paid a few extra dollars for ePacket so it didnt take 6 weeks to get here)


There is a cheaper HopeRF95W module, which is single band on 868MHz ( or 915MHz), which may be a cheaper option for some people, but it appears to be a partial clone of the official LoRa chip (SX127x) by Semtech, and as far as I can tell most libraries seem to support both the HopeRF and Semtech devices, which leads me to believe that the HopeRF device has replicated the register addresses etc of the Semtech, but perhaps as a subset of the Semtech.


Actually, buying the SX1278 was a bit of a mistake, as I thought it was a superset of the more expensive SX1276, however it is not.

SX1276 is quad band which additionally covers 868mHz and 915MHz which is used for LoRaWAN gateways which seem to be springing uo everywhere.

So I have now ordered 2 of the SX1276 modules, ( which cost more then 4 SX1278's)

In the mean time I will continue testing with the SX1278 and will probably try to get LoRaWAN working on these modules, but i will need to run my own gateway

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RogerClark
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Re: LoRa modules (AI Thinker Ra-01, SX1278)

Post by RogerClark » Sun Nov 12, 2017 8:35 pm

Just a quick update

The HopeRF95W appears seems to operate on the 868MHz and 915Mhz bands, ( http://www.hoperf.com/upload/rf/RFM95_96_97_98W.pdf )
And it seems popular with the ESP8266 to act as a LoRaWAN gateway..

The cheapest I can find these on AliExpress is $6.99 USD including shipping

Where as SX1278 based modules, like the Ra-01 modules I bought are only $3.40 USD including shipping

So it seems there is a significant premium for being able to operate on the 868 and 915 Mhz bands
I can understand this in terms of the complexity of a device that operates at twice the frequency, however I wonder if the premium is partially because LoRaWAN seems to predominately work on 868Mhz and 915Mhz


Edit.

I have now looked at the datasheets for the Semtech SX127x and the HopeRF95x and the Hope datasheet register map looks like its a complete rip off of the Semtech datasheet, with some minor changes to some of the descriptions, where they have edited the text for SX1276/77/78/79 and replaced it with RFM95/96/97/98(W)

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Squonk42
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Re: LoRa modules (AI Thinker Ra-01, SX1278)

Post by Squonk42 » Mon Nov 13, 2017 5:47 am

RogerClark wrote:
Sun Nov 12, 2017 8:35 pm
Edit.

I have now looked at the datasheets for the Semtech SX127x and the HopeRF95x and the Hope datasheet register map looks like its a complete rip off of the Semtech datasheet, with some minor changes to some of the descriptions, where they have edited the text for SX1276/77/78/79 and replaced it with RFM95/96/97/98(W)
Semtech lists Hoperf as one of their partners:
http://www.semtech.com/wireless-rf/wireless-solutions/

Please check this thread:
https://lowpowerlab.com/forum/rf-range- ... es-or-not/

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RogerClark
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Re: LoRa modules (AI Thinker Ra-01, SX1278)

Post by RogerClark » Mon Nov 13, 2017 9:03 am

@Squonk42

Thanks

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mrburnette
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Re: LoRa modules (AI Thinker Ra-01, SX1278)

Post by mrburnette » Tue Nov 14, 2017 1:49 pm

I just received two ESP32 based LoRa units from AliExpress. These were more pricey at $15 U.S.D. but I received them in 2 weeks. The pricing has increased a little since my order, but "free" shipping is now being offered.

2pcs 868MHz 915MHz SX1276 ESP32 LoRa OLED

Image

Ray

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RogerClark
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Re: LoRa modules (AI Thinker Ra-01, SX1278)

Post by RogerClark » Tue Nov 14, 2017 7:43 pm

Thanks Ray!

I noticed someone posted about them on TheThingsNetwork.

At $15 they are good value, because the RFM95W LoRa module on its its own is around $6, and the SX1276 is even more expensive ( if it uses that device)

I should order some

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RogerClark
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Re: LoRa modules (AI Thinker Ra-01, SX1278)

Post by RogerClark » Tue Nov 14, 2017 9:06 pm

Ray

I just ordered some of those



https://www.aliexpress.com/item/2pcs-86 ... 47451.html

I think it may be the same vendor, though the price seems to vary a bit.

When I looked an hour ago it was $33 and now its $32

Perhaps the USD fell slightly against the Yen, and the underlying price could be Yen.

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RogerClark
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Re: LoRa modules (AI Thinker Ra-01, SX1278)

Post by RogerClark » Tue Nov 14, 2017 9:35 pm

BTW.

One thing to note. I see some other ESP32 LoRa modules on AliExpress , which are the same price, but use the SX1278 LoRa module

Do not buy these.
The SX2178 is a subset of the SX1276 and does not operate on the frequencies normally used for LoRaWAN

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mrburnette
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Re: LoRa modules (AI Thinker Ra-01, SX1278)

Post by mrburnette » Tue Nov 14, 2017 11:29 pm

I had a play today, goal was just to xfer packets and program the ESP32 using the ArduinoIDE:

TX sketch

RX sketch


SSD1306 was from Adafruit.
U8x8lib.h was from https://github.com/olikraus/u8g2

Yes, I did purposely mix up the libs to test a few different libs.

ESP32 core is from https://github.com/espressif/arduino-esp32

Ray

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RogerClark
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Re: LoRa modules (AI Thinker Ra-01, SX1278)

Post by RogerClark » Tue Nov 14, 2017 11:41 pm

Ray

Are you sending LoRaWAN packets or raw ones.

I've noticed that some libraries e.g. RadioHead seem to have their own packet header system

I've been using Sandeep Mistry's Arduino LoRa library, which seems to send raw packets

One thing I noticed so far is the max packet size seems to be 256, though I thought the LoRa spec claimed longer packet sizes

Also, my SX1278 devices don't seem to transmit on on their full range of frequencies

I tried 434.000 and that worked fine, but I could not detect any transmission when I changed the frequency to 300Mhz
Note. This is purely for test purposes with no antenna attached.

I'm using a SDR receiver dongle (TV dongle) and also a "scanner" radio.

SDR is the most interesting as you can see the how long it transmits and also the spectrum width etc

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