Anyone using/tried the E28-2G4M27S 2.4Ghz LoRa SX1280 27dB module?
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@NeverDie no. It doesn’t screw into anything. It is fixed. It cannot be turned without turning the entire cable. Hence the male is the one doing the screwing. The male variant can turn without turning the cable.
@mfalkvidd Thanks! It finally makes sense now that you've explained it like that.
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Which thickness of coax cable should one prefer? Is thicker generally better? For instance, here are two connector cables of the same type, and both 50 ohm, but one is 0.81mm coax, and the other is 1.13mm coax. Does the difference matter?
https://www.amazon.com/gp/product/B098QGFZ2J/ref=crt_ewc_title_dp_3?ie=UTF8&psc=1&smid=AODZVW3FCSGNT
https://www.amazon.com/gp/product/B098QF5XF8/ref=crt_ewc_title_dp_1?ie=UTF8&psc=1&smid=AODZVW3FCSGNT
[Edit: I do notice that they have different IPEX connectors, but I'm wondering just about the coax diameter.]
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I'll see it through to the end, but I think at this point Ebyte 2.4Ghz LoRa is now academic. With all this antenna nonsense getting in the way of a simple, inexpensive solution, it just doesn't hold a candle to a fully integrated solution, like this simple, compact LoRa gateway, where even a simple spring antenna is sufficient:
The shield on top can be demounted and is a fully-standalone atmega328p driving the LoRa radio, which makes for a complete solution that's not much larger than the AI-Thinker module itself! I'll just drop a 915Mhz Ai-Thinker LoRa module into place instead of the 433Mhz module currently there, and, bang, it should "just work."
I suppose desoldering the IPEX connector on the EBYTE module I could perhaps make a short jumper run from a custom PCB onto the EBYTE antenna pad..... Hmmm.... Kludgy, but it might work. In contrast, however, with the AI-Thinker modules there's a through-hole already set aside for a whip antenna.
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Which thickness of coax cable should one prefer? Is thicker generally better? For instance, here are two connector cables of the same type, and both 50 ohm, but one is 0.81mm coax, and the other is 1.13mm coax. Does the difference matter?
https://www.amazon.com/gp/product/B098QGFZ2J/ref=crt_ewc_title_dp_3?ie=UTF8&psc=1&smid=AODZVW3FCSGNT
https://www.amazon.com/gp/product/B098QF5XF8/ref=crt_ewc_title_dp_1?ie=UTF8&psc=1&smid=AODZVW3FCSGNT
[Edit: I do notice that they have different IPEX connectors, but I'm wondering just about the coax diameter.]
@NeverDie The characteristic impedance of the coax is what matters. And that is all determined by the construction, which includes the thickness, but also other things, like what dielectric, and probably even what metal is used. (I don't know all the variables that they have to play with.)
So it could be that both of those options you posted are fine. But buying stuff like this on Amazon, especially through third parties is a crap shoot. No telling if it will be good or not, and the reviews aren't usually very helpful, either, on RF stuff. Not saying you shouldn't do it - I will gamble myself, but just go in fully aware that your chances of getting something shoddy are good, and make sure the price you pay is worth the gamble.
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@NeverDie The characteristic impedance of the coax is what matters. And that is all determined by the construction, which includes the thickness, but also other things, like what dielectric, and probably even what metal is used. (I don't know all the variables that they have to play with.)
So it could be that both of those options you posted are fine. But buying stuff like this on Amazon, especially through third parties is a crap shoot. No telling if it will be good or not, and the reviews aren't usually very helpful, either, on RF stuff. Not saying you shouldn't do it - I will gamble myself, but just go in fully aware that your chances of getting something shoddy are good, and make sure the price you pay is worth the gamble.
@ejlane Agreed. Where is it that you prefer to shop?
A lot of the amazon stuff is the same as what one might find on Aliexpress, but the difference is I can get it fast and with free shipping from Amazon, and returns are a breeze. When it comes to quality, I think Mouser or Digikey usually has the best, but at usually higher prices even before you figure in shipping. Is there anywhere else worth considering? Maybe there's a good resource I've overlooked.
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@ejlane Agreed. Where is it that you prefer to shop?
A lot of the amazon stuff is the same as what one might find on Aliexpress, but the difference is I can get it fast and with free shipping from Amazon, and returns are a breeze. When it comes to quality, I think Mouser or Digikey usually has the best, but at usually higher prices even before you figure in shipping. Is there anywhere else worth considering? Maybe there's a good resource I've overlooked.
@NeverDie I think you've pretty much covered it. Yes, sometimes there's no good hobby-level alternative to Amazon/Aliexpress if you want it cheap.
Though someplace like SparkFun or Adafruit can be good for hobbyists, though you'll pay for it.
Along with Mouser and Digikey, sometimes I have good luck with Arrow or Newark. But really, it's nice to do a search with octopart.com or findchips.com if you have a pretty good idea of what you want. They will look at lots of vendors, even some that might be shading towards gray market. Can really save some time, and sometimes find things that I never would have otherwise. Saved me a few months ago on a customer project that would have otherwise had to be completely redesigned.
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Reporting back: Today I received proper IPEX to RP-SMA connector cable. I hooked up both the transmitter and receiver using them to the factory recommended 2.4ghz antennas. The transmitter and receiver are two rooms apart, and the signal has to pass through two closed doors. What I'm getting doesn't look great:
4s PacketError,RSSI,-74dBm,SNR,-4dB,Length,23,Packets,0,Errors,1,IRQreg,8052,IRQ_RX_DONE,IRQ_HEADER_VALID,IRQ_CRC_ERROR,IRQ_PREAMBLE_DETECTED 7s PacketError,RSSI,-79dBm,SNR,-15dB,Length,23,Packets,0,Errors,2,IRQreg,8052,IRQ_RX_DONE,IRQ_HEADER_VALID,IRQ_CRC_ERROR,IRQ_PREAMBLE_DETECTED 9s PacketError,RSSI,-77dBm,SNR,-11dB,Length,23,Packets,0,Errors,3,IRQreg,8052,IRQ_RX_DONE,IRQ_HEADER_VALID,IRQ_CRC_ERROR,IRQ_PREAMBLE_DETECTED 12s PacketError,RSSI,-73dBm,SNR,-1dB,Length,23,Packets,0,Errors,4,IRQreg,8052,IRQ_RX_DONE,IRQ_HEADER_VALID,IRQ_CRC_ERROR,IRQ_PREAMBLE_DETECTED 13s Hello World 1234567890*,CRC,DAAB,RSSI,-78dBm,SNR,-6dB,Length,23,Packets,1,Errors,4,IRQreg,8012 14s PacketError,RSSI,-79dBm,SNR,-8dB,Length,23,Packets,1,Errors,5,IRQreg,8052,IRQ_RX_DONE,IRQ_HEADER_VALID,IRQ_CRC_ERROR,IRQ_PREAMBLE_DETECTED 16s PacketError,RSSI,-78dBm,SNR,-4dB,Length,23,Packets,1,Errors,6,IRQreg,8052,IRQ_RX_DONE,IRQ_HEADER_VALID,IRQ_CRC_ERROR,IRQ_PREAMBLE_DETECTED 18s PacketError,RSSI,-82dBm,SNR,-17dB,Length,23,Packets,1,Errors,7,IRQreg,8052,IRQ_RX_DONE,IRQ_HEADER_VALID,IRQ_CRC_ERROR,IRQ_PREAMBLE_DETECTED 26s PacketError,RSSI,-80dBm,SNR,-22dB,Length,23,Packets,1,Errors,8,IRQreg,8020,IRQ_HEADER_ERROR,IRQ_PREAMBLE_DETECTED 28s PacketError,RSSI,-79dBm,SNR,-9dB,Length,23,Packets,1,Errors,9,IRQreg,8052,IRQ_RX_DONE,IRQ_HEADER_VALID,IRQ_CRC_ERROR,IRQ_PREAMBLE_DETECTED 31s PacketError,RSSI,-85dBm,SNR,-19dB,Length,23,Packets,1,Errors,10,IRQreg,8052,IRQ_RX_DONE,IRQ_HEADER_VALID,IRQ_CRC_ERROR,IRQ_PREAMBLE_DETECTED 32s PacketError,RSSI,-83dBm,SNR,-7dB,Length,23,Packets,1,Errors,11,IRQreg,8052,IRQ_RX_DONE,IRQ_HEADER_VALID,IRQ_CRC_ERROR,IRQ_PREAMBLE_DETECTED 35s Hello World 1234567890*,CRC,DAAB,RSSI,-77dBm,SNR,-8dB,Length,23,Packets,2,Errors,11,IRQreg,8012 37s PacketError,RSSI,-82dBm,SNR,-15dB,Length,23,Packets,2,Errors,12,IRQreg,8052,IRQ_RX_DONE,IRQ_HEADER_VALID,IRQ_CRC_ERROR,IRQ_PREAMBLE_DETECTED 50s Hello World 1234567890*,CRC,DAAB,RSSI,-81dBm,SNR,-17dB,Length,23,Packets,3,Errors,12,IRQreg,8012 51s Hello World 1234567890*,CRC,DAAB,RSSI,-81dBm,SNR,-12dB,Length,23,Packets,4,Errors,12,IRQreg,8012 54s PacketError,RSSI,-79dBm,SNR,-4dB,Length,23,Packets,4,Errors,13,IRQreg,8052,IRQ_RX_DONE,IRQ_HEADER_VALID,IRQ_CRC_ERROR,IRQ_PREAMBLE_DETECTED 57s Hello World 1234567890*,CRC,DAAB,RSSI,-74dBm,SNR,-6dB,Length,23,Packets,5,Errors,13,IRQreg,8012 60s PacketError,RSSI,-78dBm,SNR,-14dB,Length,23,Packets,5,Errors,14,IRQreg,8052,IRQ_RX_DONE,IRQ_HEADER_VALID,IRQ_CRC_ERROR,IRQ_PREAMBLE_DETECTED 62s Hello World 1234567890*,CRC,DAAB,RSSI,-75dBm,SNR,-6dB,Length,23,Packets,6,Errors,14,IRQreg,8012 67s PacketError,RSSI,-84dBm,SNR,-20dB,Length,23,Packets,6,Errors,15,IRQreg,8052,IRQ_RX_DONE,IRQ_HEADER_VALID,IRQ_CRC_ERROR,IRQ_PREAMBLE_DETECTED 69s PacketError,RSSI,-78dBm,SNR,-12dB,Length,23,Packets,6,Errors,16,IRQreg,8052,IRQ_RX_DONE,IRQ_HEADER_VALID,IRQ_CRC_ERROR,IRQ_PREAMBLE_DETECTED 72s Hello World 1234567890*,CRC,DAAB,RSSI,-77dBm,SNR,-11dB,Length,23,Packets,7,Errors,16,IRQreg,8012 76s PacketError,RSSI,-79dBm,SNR,-13dB,Length,23,Packets,7,Errors,17,IRQreg,8052,IRQ_RX_DONE,IRQ_HEADER_VALID,IRQ_CRC_ERROR,IRQ_PREAMBLE_DETECTED 78s Hello World 1234567890*,CRC,DAAB,RSSI,-79dBm,SNR,-12dB,Length,23,Packets,8,Errors,17,IRQreg,8012 80s Hello World 1234567890*,CRC,DAAB,RSSI,-76dBm,SNR,-7dB,Length,23,Packets,9,Errors,17,IRQreg,8012 83s PacketError,RSSI,-75dBm,SNR,-7dB,Length,23,Packets,9,Errors,18,IRQreg,8052,IRQ_RX_DONE,IRQ_HEADER_VALID,IRQ_CRC_ERROR,IRQ_PREAMBLE_DETECTED 86s PacketError,RSSI,-78dBm,SNR,-6dB,Length,23,Packets,9,Errors,19,IRQreg,8052,IRQ_RX_DONE,IRQ_HEADER_VALID,IRQ_CRC_ERROR,IRQ_PREAMBLE_DETECTED 103s PacketError,RSSI,-76dBm,SNR,-18dB,Length,23,Packets,9,Errors,20,IRQreg,8052,IRQ_RX_DONE,IRQ_HEADER_VALID,IRQ_CRC_ERROR,IRQ_PREAMBLE_DETECTED 105s PacketError,RSSI,-81dBm,SNR,-18dB,Length,23,Packets,9,Errors,21,IRQreg,8052,IRQ_RX_DONE,IRQ_HEADER_VALID,IRQ_CRC_ERROR,IRQ_PREAMBLE_DETECTED 108s PacketError,RSSI,-79dBm,SNR,-3dB,Length,23,Packets,9,Errors,22,IRQreg,8052,IRQ_RX_DONE,IRQ_HEADER_VALID,IRQ_CRC_ERROR,IRQ_PREAMBLE_DETECTED 109s Hello World 1234567890*,CRC,DAAB,RSSI,-78dBm,SNR,-3dB,Length,23,Packets,10,Errors,22,IRQreg,8012 110s Hello World 1234567890*,CRC,DAAB,RSSI,-79dBm,SNR,-6dB,Length,23,Packets,11,Errors,22,IRQreg,8012 112s PacketError,RSSI,-78dBm,SNR,-3dB,Length,23,Packets,11,Errors,23,IRQreg,8052,IRQ_RX_DONE,IRQ_HEADER_VALID,IRQ_CRC_ERROR,IRQ_PREAMBLE_DETECTEDI think maybe the breadboard construction and long wires are introducing too much unwanted signals, resulting in lowered performance. The only way I can think of to get rid of that would be to make a specialty PCB that puts an atmega328p in close proximity with the module, so that there aren't long wires or long traces to pick up noise along the way.Or, maybe it's something else. In any case, I'm going to pause this and switch-over to a 915Mhz AI-Thinker module to see whether I get more traction there. -
Re-thinking this, probably the easiest way to exclude whether or not the breadboarding and related wiring is a crippling source of noise would be to create a PCB that an Arduino Pro Mini can dock with and which makes all the needed connections directly to the E28-2G4M27S. It's so easy that I should have thought of it in the first place! I have started work on it, and I'll post a rendering when its ready. I may post it in openhardware.io, and I think I may take a similar approach to future breakout boards as well. Pro-mini's are so cheap that it will make for a good way to test different radio modules.
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What happened to prices? I checked just now and pro mini's are selling for $5+. Pre-pandemic they could be had for closer to $1.
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What happened to prices? I checked just now and pro mini's are selling for $5+. Pre-pandemic they could be had for closer to $1.
@NeverDie Haven't you heard of the chip shortage? It's changed everything, and prices for those things that are even available have generally gone up. (Though somehow magically, the ESP32 seems to be pretty much untouched. You can still buy them, and prices have been relatively stable. I don't know how they've done it.) AVR, PIC, STM chips have all been hard to get specific models, and at times any model that has the features. I expect other brands were similar, but those are the ones that I've looked for.
I hope they someday go back, but for the foreseeable future, expect it to be like this.
Pro minis for close to $1 was always a shock, since even at 1k qty, just the chip itself costs more than that. So to get to that price for the whole assembled board, there must be some kind of gray-market thing going on. If I were to try to make a profit on 1k at a time, assembled and everything, I'm pretty sure the final price would have to be in the ballpark of $10 each.
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@NeverDie Haven't you heard of the chip shortage? It's changed everything, and prices for those things that are even available have generally gone up. (Though somehow magically, the ESP32 seems to be pretty much untouched. You can still buy them, and prices have been relatively stable. I don't know how they've done it.) AVR, PIC, STM chips have all been hard to get specific models, and at times any model that has the features. I expect other brands were similar, but those are the ones that I've looked for.
I hope they someday go back, but for the foreseeable future, expect it to be like this.
Pro minis for close to $1 was always a shock, since even at 1k qty, just the chip itself costs more than that. So to get to that price for the whole assembled board, there must be some kind of gray-market thing going on. If I were to try to make a profit on 1k at a time, assembled and everything, I'm pretty sure the final price would have to be in the ballpark of $10 each.
@ejlane & @NeverDie: Amazing technology that was available for $1 was … too hard to believe. Even $5 for a ProMini is pretty mind-blowing. Not that I buy commodities, I do buy these components a dozen at a time to save on shipping even when it is ‘free’. I laugh at myself when I spend a week of my time on a $2 chip and then wonder how I can rework it from a PCB (never worth the attempt). Compared to any other hobby or habit this radio-electronic stuff is cheaper than cooking top-ramen at home.
BTW, thanks for the radio discussion posted last week. I will read and learn later. -
Here's the schematic for what I have in mind:
Thinking about it more, I don't think it makes sense to post it to openhardware.io until I've proven that it provides a big improvement over the breadboard, because if it turns out that it isn't an improvement, it might be drawing attention away from more worthy projects.
Anyhow, I'll most likely use a similar method for building a test setup for the 915Mhz Thinker-AI radio, as it's ultimately more robust and less clumsy than breadboarding. In the meantime though I'll be breadboarding some old school 915Mhz LoRa modules to see whether going down that path is likely to bear fruit or not.
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So as to have a point of comparison, I today hooked up some old school SX1276 915Mhz LoRa modules (based on an Adafruit breakout board: https://www.adafruit.com/product/3072?gclid=EAIaIQobChMIxJm5r6-w9wIV_WxvBB0GjwCCEAQYASABEgLRofD_BwE ), and the difference is like night and day in performance:
At the same distance as with previous tests, it works 100% flawlessly:377s Hello World 1234567890*,CRC,DAAB,RSSI,-74dBm,SNR,10dB,Length,23,Packets,108,Errors,0,IRQreg,50 378s Hello World 1234567890*,CRC,DAAB,RSSI,-74dBm,SNR,9dB,Length,23,Packets,109,Errors,0,IRQreg,50 379s Hello World 1234567890*,CRC,DAAB,RSSI,-74dBm,SNR,10dB,Length,23,Packets,110,Errors,0,IRQreg,50 381s Hello World 1234567890*,CRC,DAAB,RSSI,-74dBm,SNR,10dB,Length,23,Packets,111,Errors,0,IRQreg,50 382s Hello World 1234567890*,CRC,DAAB,RSSI,-74dBm,SNR,10dB,Length,23,Packets,112,Errors,0,IRQreg,50 383s Hello World 1234567890*,CRC,DAAB,RSSI,-74dBm,SNR,9dB,Length,23,Packets,113,Errors,0,IRQreg,50 384s Hello World 1234567890*,CRC,DAAB,RSSI,-74dBm,SNR,9dB,Length,23,Packets,114,Errors,0,IRQreg,50 385s Hello World 1234567890*,CRC,DAAB,RSSI,-74dBm,SNR,9dB,Length,23,Packets,115,Errors,0,IRQreg,50 386s Hello World 1234567890*,CRC,DAAB,RSSI,-74dBm,SNR,9dB,Length,23,Packets,116,Errors,0,IRQreg,50 387s Hello World 1234567890*,CRC,DAAB,RSSI,-74dBm,SNR,9dB,Length,23,Packets,117,Errors,0,IRQreg,50 388s Hello World 1234567890*,CRC,DAAB,RSSI,-74dBm,SNR,9dB,Length,23,Packets,118,Errors,0,IRQreg,50 389s Hello World 1234567890*,CRC,DAAB,RSSI,-74dBm,SNR,9dB,Length,23,Packets,119,Errors,0,IRQreg,50 390s Hello World 1234567890*,CRC,DAAB,RSSI,-74dBm,SNR,9dB,Length,23,Packets,120,Errors,0,IRQreg,50 391s Hello World 1234567890*,CRC,DAAB,RSSI,-74dBm,SNR,9dB,Length,23,Packets,121,Errors,0,IRQreg,50 392s Hello World 1234567890*,CRC,DAAB,RSSI,-74dBm,SNR,9dB,Length,23,Packets,122,Errors,0,IRQreg,50 394s Hello World 1234567890*,CRC,DAAB,RSSI,-74dBm,SNR,10dB,Length,23,Packets,123,Errors,0,IRQreg,50 395s Hello World 1234567890*,CRC,DAAB,RSSI,-74dBm,SNR,9dB,Length,23,Packets,124,Errors,0,IRQreg,50 396s Hello World 1234567890*,CRC,DAAB,RSSI,-74dBm,SNR,9dB,Length,23,Packets,125,Errors,0,IRQreg,50 397s Hello World 1234567890*,CRC,DAAB,RSSI,-75dBm,SNR,10dB,Length,23,Packets,126,Errors,0,IRQreg,50 398s Hello World 1234567890*,CRC,DAAB,RSSI,-71dBm,SNR,10dB,Length,23,Packets,127,Errors,0,IRQreg,50 399s Hello World 1234567890*,CRC,DAAB,RSSI,-74dBm,SNR,10dB,Length,23,Packets,128,Errors,0,IRQreg,50 400s Hello World 1234567890*,CRC,DAAB,RSSI,-73dBm,SNR,9dB,Length,23,Packets,129,Errors,0,IRQreg,50 401s Hello World 1234567890*,CRC,DAAB,RSSI,-75dBm,SNR,9dB,Length,23,Packets,130,Errors,0,IRQreg,50 402s Hello World 1234567890*,CRC,DAAB,RSSI,-74dBm,SNR,10dB,Length,23,Packets,131,Errors,0,IRQreg,50which, quite frankly, is what I had been expecting from the 2.4GHz modules. Notice that these are also on breadboards, yet the SNR is vastly superior to what the Ebyte modules were reporting. So, although I can't yet say so definitively, I'm starting to suspect that there's something wrong with the Ebyte 2.4Ghz LoRa modules that I received. If I had a couple 2.4Ghz LoRa modules from a different manufacturer, it might tell the tale. As it stands, it doesn't much matter the reason, since performance at 915Mhz is so much better.
I'll next try running the Ebyte modules direct from two AA batteries. If there's noise in the present power supplies, that should remove it. I've already put decoupling caps on the radio module, but I could also do the same with the Arduino Pro Mini. Sooner or later we'll find the culprit. If worse comes to worst, I'll fabricate this low noise test board and try it with that:
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Semtech did write a paper analyzing possible interference between the SX1280 LoRa and WiFi. Here is the conclusion:
Not exactly sure what it means. Looks as though it doesn't have as much immunity to 802.11n as to 802.11g, which is maybe(?) a problem given how common 802.11n is these days. Reducing bandwidth and increasing spreading factor are the recommended workarounds. Unfortunately, all my neighbors have wi-fi, so finding unused spectrum, or with low enough signal, may not be feasible at 2.4Ghz.
Come to think of it, I do have a dual-band meshed wi-fi network at home. I hadn't thought I needed tri-band, but this might be a case where backhauling over that third band, or possibly ethernet, might knock down some of the wi-fi generated "noise" in the 2.4Ghz spectrum. If this turns out to be part of the issue, then, indeed, going to 915Mhz instead would be a lot easier solution.
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One more reason for preferring 915Mhz over 2.4Ghz: The SX1262 (915Mhz) has a receive sensitivity of -148dBm, whereas the SX1280 (2.4Ghz) is only -132dBm. I hadn't realized the gap was so large. All by itself that's an appreciable difference. I suspect that to cash-in on all the potential receive sensitivity, it may require a TCXO, but I'd have to look that up to be sure. Now granted, external PA's and LNA's might be employed, but as far as the chips themselves, the max transmit power on the SX1280 is 12.5dBm, whereas on the SX1262, it's 22dBm, so at the chip level the SX1262 is more capable on the transmit side by a considerable degree.
Comparing the SX1262 to the SX1276 (Adafruit that I tested today), the receive sensitivities are the same. The SX1276 has a max Tx power of 20dBm, so the SX1262's 22dBm transmit power is only just a little better. The SX1262 may be more energy efficient, but in terms of raw link budget, it's almost the same as the SX1276. So, for some applications, such as gateways, using SX1276 chips/modules might make sense if they're cheaper. However, looking at current market pricing, they don't appear to be. Strange.
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Reporting back: I tried running both transceivers off of two AA's with decoupling capacitors and... no change. I also tried varying the location, in case there was a strong local interference source. No change. Again, to recap: RSSI seems good, but SNR seems bad. So, the next thing left to try is the low noise PCB I pictured above. I'll do that, but fabrication will have to wait until I have other PCB's ready to be fabbed as well so as to save on shipping by combining the orders, because at this point getting these Ebyte SX1280 modules to work satisfactorily is looking more and more like a long shot. :disappointed: Given that Andreas Spiess was also not particularly sanguine about his Ebyte SX1280 LoRa modules, I suspect the blame may lay with the modules. Anyhow, it's becoming academic, because I'm moving on to 915Mhz LoRa, since from what I've seen firsthand so far that seems much more robust, and on paper an SX1262 or SX1276 handily outperforms an SX1280.
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@mfalkvidd Good catch! I'll take your word for it. Thank you!
Reporting back: I found a critical error. The library defaults to leaving the TX_EN and RX_EN pins disconnected. However, this module has a PA and LNA, so it is relevant to it. Since my first attempt merely followed the wiring instructions in the library, I had failed to enable these pins. Now that I have, it's a big improvement.
@NeverDie Hi, I've just started playing with a pair of these modules that I've had kicking around for a while. Fascinating thread and I haven't finished reading through yet, thanks for being so thorough!
I'm using the same library. When it comes to enabling the TX_EN and RX_EN pins, can you clarify how? Is it done through the microcontroller script, or by setting the pin inputs to high (+3.3v)?
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@NeverDie Hi, I've just started playing with a pair of these modules that I've had kicking around for a while. Fascinating thread and I haven't finished reading through yet, thanks for being so thorough!
I'm using the same library. When it comes to enabling the TX_EN and RX_EN pins, can you clarify how? Is it done through the microcontroller script, or by setting the pin inputs to high (+3.3v)?
@samh For the receiver node, I simply wired RX_EN to 3.3V and TX_EN to GND. For the transmitter module, I found that wiring TX_EN direcctly to 3.3V doesn't work so well (probably too high a duty cycle for the PA to be operating continuously like that), so I instead wired TX_EN to a spare pin and I modified the code so as to drive that pin HIGH just prior to transmitting and drive it to LOW when done transmitting. Also, on the transmitter node I wired RX_EN to ground. This seemed to work. However, it reminds me now that this was really just improvisation on my part for expediency in getting something setup fast.. Perhaps I should be using pull-up and/or pull-down resistors instead. Thanks for bringing up this topic! I'll investigate further. Please do post what you end up using youself, as well as whether you are getting similar or different results regarding noise (SNR) and/or range.
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Reporting back: It turns out that in the settings.h file, you can assign pins for TX_EN and RX_EN. I assigned Arduino pin 4 for TX_EN and pin 5 for RX_EN, and it works fine.
I also inserted 10K resistors as a "just in case". I also increased TX_POWER to 10.
I'm not sure which of the 3 changes made the most difference, but the result is noticeable improvement. SNR is still reported as low., but I am now getting reliable longer range than previously. Maybe SNR is just not measured accurately by the module?
IIRC, the module has two forms of integrated step-down within the chip: an LDO and a buck converter. Not sure which one the library defaults to (I'll have to look it up) but if it's the buck, then switching over to the LDO might help with the SNR.
[Edit: I just now checked, and the library defaults to using the LDO rather than the buck converter]
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Last update: I changed frequencies to 2.42Ghz, and SNR became a bit better, so maybe interference in the 2.4Ghz band really does play a role. It still performs much worse than the 915Mhz LoRa nodes I i discussed above however. At this point the next noticeable improvement, if anything, probably won't happen until I fab the custom low noise PCB which I showed above.
