(12-17-2020, 11:40 AM)notpod Wrote: HAM RADIO guy here. I like what I read, Will think about this some more. And we have LoRa options now...
Hi notpod, I am a ham too, sadly I no longer give my callsign online on forums thought outside of arranging direct over the air contact stuff.
LoRa is great(aside from not being a free/libre protocol same problem with D-STAR) for commercial off the shelf components, I prefer hacks based on WSPR or other fully open psk/fsk protocols.
I like POCSAG though as it is both an established universal unlicensed(for the user) commercial service which can also be used by radio amateurs who have configured the local repeater or station with free/libre software tools for paging using modified or programmable to our bands COTS pagers.
I appreciate the interest, I am stopped for now trying to find a good ultra low power reference receiver IC for a dev kit for software devs without tearing apart pagers.
07-20-2021, 03:14 AM
(This post was last modified: 07-20-2021, 04:28 AM by biketool.)
I took a look at this IC, what do you all think about this as the receiver, since it has a TX function too it could be used to do many other things(especially if we bypass our POCSAG mode band-passes) including short range paging other Pinephones(or pagers), WSPR, or LoRa, maybe even FM audio tx for older cars(though the datasheet says FSK is the tx mode); perhaps a switchable power TX amp for greater range for licensed amateur radio ops on their freqs. If we can do that POCSAG will just be one function(will need another decoder than just the POCSAG hardware decoder IC, maybe an i2c sound card?) of a very useful pogo-pin add on without needing to go full HackRF.
https://www.ti.com/lit/ds/symlink/cc1000.pdf
I have not been able to move forward without this key IC but together I think we could start populating a breadboard once I hear some comments, my main concern is sensitivity though a LNA preamp might help while burning power.
Since this would require a controller anyways to keep power down I think my go-to attiny85 could bridge the i2c needs of both the RF transceiver and the decoder chips; also a very stable crystal so we can do more freq sensitive stuff than just wider band POCSAG signals.
Input from experienced RF engineers is key to choosing a good IC candidate as my experience with radio design is almost exclusively power hungry SDRs or discreet component QRP sets maybe with a DDS for HF that may not be as efficient, small, or sensitive as we will want for this project and all have had high part count.
(07-20-2021, 03:14 AM)biketool Wrote: I took a look at this IC, what do you all think about this as the receiver, since it has a TX function too it could be used to do many other things(especially if we bypass our POCSAG mode band-passes) including short range paging other Pinephones(or pagers), WSPR, or LoRa, maybe even FM audio tx for older cars(though the datasheet says FSK is the tx mode); perhaps a switchable power TX amp for greater range for licensed amateur radio ops on their freqs. If we can do that POCSAG will just be one function(will need another decoder than just the POCSAG hardware decoder IC, maybe an i2c sound card?) of a very useful pogo-pin add on without needing to go full HackRF.
https://www.ti.com/lit/ds/symlink/cc1000.pdf
I have not been able to move forward without this key IC but together I think we could start populating a breadboard once I hear some comments, my main concern is sensitivity though a LNA preamp might help while burning power.
Since this would require a controller anyways to keep power down I think my go-to attiny85 could bridge the i2c needs of both the RF transceiver and the decoder chips; also a very stable crystal so we can do more freq sensitive stuff than just wider band POCSAG signals.
Input from experienced RF engineers is key to choosing a good IC candidate as my experience with radio design is almost exclusively power hungry SDRs or discreet component QRP sets maybe with a DDS for HF that may not be as efficient, small, or sensitive as we will want for this project and all have had high part count.
Check this out: https://hackaday.com/2021/05/18/send-old...-hardware/
and https://www.soldierx.com/bbs/202105/Pock...ransmitter
Seems like using HopeRF RFM23BPW module. HopeRF is the company who teachs Pine64 on the Lora module design and tuning :-)
For the i2C to SPI protocol conversion TinyAVR design, just follow the PinePhone finger print back cover code and here is the link: https://github.com/zschroeder6212/tiny-i2c-spi
08-08-2021, 12:55 AM
(This post was last modified: 08-08-2021, 01:17 AM by biketool.)
(08-07-2021, 10:25 PM)tllim Wrote: (07-20-2021, 03:14 AM)biketool Wrote: (snip)
Check this out: https://hackaday.com/2021/05/18/send-old...-hardware/
and https://www.soldierx.com/bbs/202105/Pock...ransmitter
Seems like using HopeRF RFM23BPW module. HopeRF is the company who teachs Pine64 on the Lora module design and tuning :-)
For the i2C to SPI protocol conversion TinyAVR design, just follow the PinePhone finger print back cover code and here is the link: https://github.com/zschroeder6212/tiny-i2c-spi
Upthread I have several cheap ways to send POCSAG pager signals below regulated power levels, for simplicity I have been using a HackRF/Portapack H1 and it gets the job done with ease and I have one handy so while I have other tx hardware I mention, it sits in boxes for now.
The RX chip looks interesting though especially if there is a partnership already with hopeRF.
Truthfully if we could do radio silent RX on both commercial POCSAG messages AND LoRa for local p2p RF messaging that would be even more useful than a one use receiver. Of course it would require other local users with LoRa for the off-grid p2p comms.
The question is if we want to invest effort in a software or hardware decoding for the POCSAG as I think that will be the more important daily driver use of the module even if we do also have LoRa.
I have over the years realized that switching a phone into a POCSAG RF silent mode should massively increase battery life so I hope that this module can be in a low power mode like an old 90s pager and still be able to reliably receive a commercial or amateur radio paging signal and usefully decode it.
(edit)
I am not sure if I see an amplified signal out pin on the RFM23BP but that was a quick look at the datasheet, we would need to have that signal form a tuned frequency if we wanted to use a hardware decoder chip, at least for the POCSAG both for power savings and I think it is more reliable to use a hardware decoder into something with memory to cache messages until the Pinephone does a wake cycle and clears that cache into incoming messages.
If we are going to be doing LoRa I think you should spec the highest quality frequency control crystal that HopeRF can provide or eeven consider resoldering a self-provided crystal as you can do some wildly low powered tight signals if you can be certian that both the rx and tx are on the same tightly tuned frequency. We might even consider WSPR mode where we could over several hours be able to transmit or receive very short messages over hundreds of km using nothing but bounces from terrain, overflying aircraft, and meteor ionization trails; though the really best way to use WSPR is to have a good external tuner and then use the WSJT decoder program on the repos over an audio line. https://www.physics.princeton.edu/pulsar/k1jt/wspr.html
Just for reference you can use even the moon as a communications satellite using WSPR protocol, a good yaggi antenna, about 100w of power(anyone who can solder can build that amp), a very stable oscillator(that crystal we were talking about and/or a GPS signal discipline injector) transmitter, and even a pinephone to decode the returning signals assuming you also have a very stable frequency receiver with another very tight yaggi or big dish antenna.
(08-08-2021, 12:55 AM)biketool Wrote: (08-07-2021, 10:25 PM)tllim Wrote: (07-20-2021, 03:14 AM)biketool Wrote: (snip)
Check this out: https://hackaday.com/2021/05/18/send-old...-hardware/
and https://www.soldierx.com/bbs/202105/Pock...ransmitter
Seems like using HopeRF RFM23BPW module. HopeRF is the company who teachs Pine64 on the Lora module design and tuning :-)
For the i2C to SPI protocol conversion TinyAVR design, just follow the PinePhone finger print back cover code and here is the link: https://github.com/zschroeder6212/tiny-i2c-spi
Upthread I have several cheap ways to send POCSAG pager signals below regulated power levels, for simplicity I have been using a HackRF/Portapack H1 and it gets the job done with ease and I have one handy so while I have other tx hardware I mention, it sits in boxes for now.
The RX chip looks interesting though especially if there is a partnership already with hopeRF.
Truthfully if we could do radio silent RX on both commercial POCSAG messages AND LoRa for local p2p RF messaging that would be even more useful than a one use receiver. Of course it would require other local users with LoRa for the off-grid p2p comms.
The question is if we want to invest effort in a software or hardware decoding for the POCSAG as I think that will be the more important daily driver use of the module even if we do also have LoRa.
I have over the years realized that switching a phone into a POCSAG RF silent mode should massively increase battery life so I hope that this module can be in a low power mode like an old 90s pager and still be able to reliably receive a commercial or amateur radio paging signal and usefully decode it.
(edit)
I am not sure if I see an amplified signal out pin on the RFM23BP but that was a quick look at the datasheet, we would need to have that signal form a tuned frequency if we wanted to use a hardware decoder chip, at least for the POCSAG both for power savings and I think it is more reliable to use a hardware decoder into something with memory to cache messages until the Pinephone does a wake cycle and clears that cache into incoming messages.
If we are going to be doing LoRa I think you should spec the highest quality frequency control crystal that HopeRF can provide or eeven consider resoldering a self-provided crystal as you can do some wildly low powered tight signals if you can be certian that both the rx and tx are on the same tightly tuned frequency. We might even consider WSPR mode where we could over several hours be able to transmit or receive very short messages over hundreds of km using nothing but bounces from terrain, overflying aircraft, and meteor ionization trails; though the really best way to use WSPR is to have a good external tuner and then use the WSJT decoder program on the repos over an audio line. https://www.physics.princeton.edu/pulsar/k1jt/wspr.html
Just for reference you can use even the moon as a communications satellite using WSPR protocol, a good yaggi antenna, about 100w of power(anyone who can solder can build that amp), a very stable oscillator(that crystal we were talking about and/or a GPS signal discipline injector) transmitter, and even a pinephone to decode the returning signals assuming you also have a very stable frequency receiver with another very tight yaggi or big dish antenna.
The PinePhone LoRa back cover samples already ready, jump PM me and I will ship one to you. Antenna design using flax PCB and still ahve room to improve.
One the crystal question, for sure needs to use low ppm type and also every production batch needs to fine tuning for optimum performance. HopeRF has provided spectrum analyzer and teach us how to tune.
On the P2P LoRa mesh, please check out Meshtastic.
Has anyone poked around with the DSP on the modem? IIRC at least one LTE channel is inside the (33cm?) HAM band and the DSP code is floating around on github. I've skimmed over it, it's definitely some kind of SDR baseband firmware (unlike the "broadcom wifi firmware" which just sat between the MAC/PHY/PC and pushed buffers around.)
(08-10-2021, 06:16 AM)swiley Wrote: Has anyone poked around with the DSP on the modem? IIRC at least one LTE channel is inside the (33cm?) HAM band and the DSP code is floating around on github. I've skimmed over it, it's definitely some kind of SDR baseband firmware (unlike the "broadcom wifi firmware" which just sat between the MAC/PHY/PC and pushed buffers around.)
VERY VERY INTERESTING!
Truth is for whatever we are doing the future is fully user controlled SDR vs black box on-silicon components.
One problem though when the US is somehow tied to a project is that apparently ITAR rules prohibit uncontrolled distribution of SDRs capable of a certain sample rate.
https://en.wikipedia.org/wiki/Internatio...egulations
It would probably only apply to designed for purpose hardware and not to a hacked driver or firmware though.
It would probably end up like some kinds of encryption which is apparently also an IRAR restricted thing yet we in the FOSS community do not seem to see any problematic enforcement.
What frequency band are the pine LoRa covers on?
I am looking at this IC PCF5001T
pdf.datasheetcatalog.com/datasheet/philips/PCF5001T.pdf
chosen based mostly on availability, I think the DI(pin 17) will work with the digital out pin from the HopeRF RFM23BPW.
The POCSAG controller has a read cycle pin which should be able to trigger wake/rx on the hopeRF IC so we might be able to save some W/h.
Thoughts?
I would LOVE to find a cheap breakout SM PCB for SOT136 packages so I don't have to hand micro-solder with magnet wire this PCF5001 and glue it down onto a perfboard.
I am assuming the Pinephone add-on is going to be a 433mhz?? It looks like I can tune the hoperf module to commercial and amateur radio 400-500 mhz area paging freqs though I hope it will work with the band passes on the board though we can bypass and change if required.
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