For the SX1262 modules I have, only power to the core is from the DC-DC converter, the PA is powered from VCC (3.3V). The net effect is that current consumption during 10dBm TX is circa 50mA, much the same as an SX1278.
The SX1261 however, does power the PA from the DC-DC converter and the data sheet claims the current consumption at 10dBm would be 14.2mA.
For a node with a low sleep current, where most all of the battery power is used for transmissions, the SX1261 could double battery life.
I would prefer not to use it in a deployment but to try the idea there’s Semtech’s own SX1261MB2BAS oddly enough US vendor Digikey has only the 868 version. I guess one could still check the TX power consumption into a dummy load, RF power meter, or DC block and attenuators stepping down to safely feed an SA, or someone really determined could change the surrounding networks, presumably the design docs include the 915 component values.
Not so keen to invest the money to test a SX1261MB2BAS, willing to accept freebies though.
I wonder if the different interface has put developers off, the SX1261/2 (and SX1280/1) are not register centric like the SX127x, but its not so difficult a change really ?
Although the silicon can be bought, its the availabilty of modules such as RFM96 etc that has a major affect on the application take up.
I’m not sure this really different on the air, vs. different in how you configure it, but it could be interesting to ask Semtech about if there’s a way to do so.
I’ve noticed that the detection of the sync word is fairly leaky in terms of mismatches still being picked up some fraction of the time by gateways; it might be interesting to do statistical tests with different values in the node and see what is most successful in being detected by a gateway with TTN’s normal public lorawan network sync word setting.
Oh I have, and the developer portal guys did say how the LoRa sync word is configured, but as far as I know there is no explanation in the data sheets. Can you spot how its done, in essense (SX126x 16bit versus SX127x 8bit)
0x3444 = 0x34
0x1424 = 0x12
I too have noticed the detection of sync word is ‘leaky’ (I do like to check these things) which you might be inclined to think is a bug or at least worthy of a proper explanation.
Hi,
As @LoRaTracker say DIO0 from SX1276 and BUSY from SX1262 has nothing in common.
SX1262 do not have DIO0 and you can program the chip to send all events on DIO1 (this is simpler than SX1271)
But SX1262 has a BUSY pin that the SX1276 do not have. The code need to know connection of BUSY pin and DIO1 pin.
I reuse the same struct for the new chip.
for SX1276 .dio is [DIO0, DIO1]
for SX1262 .dio is [BUSY, DIO1]
The values are not used the same way in the library depending on which radio module is define for object radio line 32.
I may have to add more explanation to the README or make two different structure (it will make the compiled library larger).
I was curious to tests the low current capability of the SX1261, the data sheet says that current consumption during transmit should be around 25mA @ 14dBm, which is under half of what I measure on a Sx127x.
Considering that most of the battery power for a TTN node would be transmit power, the SX1261 promises to save you all that faff chasing very low sleep currents, which have a very marginal effect on battery life. Use a SX1261 and potentially you could double battery life.
I could not find a SX1261 module so I swapped the SX1262 on one of my modules for a SX1261 IC. Current consumption during TX for this modified module is around 35% lower than a SX127x. It would be unfair to give an exact figure, since I dont known if the switching inductor on the SX1262 module was the right part to power the PA on the SX1261.
Sleep current of the SX1261\62 is around half that of a SX127x, at 5mA.
Anyone know of a SX1261 module in the style of the RFM96 etc ?
What i understand based on Semtech datasheet in case of SX1262 to reach the 22dBm output the PA needs 3.3V (3.1V on schematic?). It means that the SX1262 module schematic should be like on the right side (REG PA direct connection to VBAT). If you have module with SX1262 but the shema is same as left side the output will not reach the 22dBm because the VDD IN for REG PA is 1.55V (it is a buck converter so it can produce lower voltage than input).
You swapped the IC on the SX1262 module to SX1261 right? I think you need to modify the connection on your PCB to the same as left side to reach the lower consumption. (Additionally the higher input voltage on REG PA means higher output voltage and it is possible to fry your low power PA in SX1261).
Thanks, it prompted me to RTFM. There is a similar diagram on pages 33+ of the datasheet.
Whether it can be modified will require a very close inspection of the module.
I would suspect that the additional inductor on the SX1261 circuit, in the PA_SUPPLY line, is to reduce switching noise getting into the PA, so for test purposes it might be possible to replace it with a wire short.
