4 ms·

Building an FM radio from $3 radio chip and an 84MHz ARM Arduino

69 points by 9wzYQbTYsAIc 4y ago

hulitu 4y ago
> Building an FM radio from $3 radio chip and an 84MHz ARM Arduino The article is great. He just forgot to explain how and why (84 Mhz microcontroller for a FM radio ? ) he did it. /s
- 9wzYQbTYsAIc 4y ago
  Another day, another hack, is the hackaday way.
- squarefoot 4y ago
  That in fact is quite overkill; probably it was what he had at hand. That FM chip can be controlled by any uC capable of bitbanging i2c, so pretty much every cheap one including small ATTiny uCs that cost one tenth of the Arduino Due.
anaganisk 4y ago
Didn’t RPI have In built capability to do that? I built a cheap streaming system, back when bluetooth wasn’t so main stream to make “piplay” for my stereo in car with Pi2.
- 9wzYQbTYsAIc 4y ago
  I’m not sure, it might. As I recall, some ARM SoC have FM radios in them. edit: ah, it was the Qualcomm modems that I was recalling https://www.wired.com/2016/07/phones-fm-chips-radio-smartphone/ https://www.wired.com/2016/07/phones-fm-chips-radio-smartpho...
- bdowling 4y ago
  Sort of. The Raspberry Pi CPU had a configurable clock generator that could output up to about 125MHz to a GPIO line. Some people figured out that it was possible to rapidly change the configuration registers to modulate an audio signal onto a carrier frequency in the FM broadcast range. [0] So you could make a low power FM transmitter using just a Raspberry Pi and a piece of wire. [0] http://www.icrobotics.co.uk/wiki/index.php/Turning_the_Raspberry_Pi_Into_an_FM_Transmitter http://www.icrobotics.co.uk/wiki/index.php/Turning_the_Raspb...
deleted 4y ago
[deleted]
amelius 4y ago
... based on the TEA5767 radio module. So this is more a lesson in how to wire things together than it is in how FM radio even works.
- teeray 4y ago
  The TEA5767 is a full FM broadcast receiver on a chip. So yeah, it’s really just how to wire up that chip, connect it to an audio amplifier (LM4811), etc. If you want to learn how radios work, I’d recommend many of the learning materials out there for amateur radio.
  - omegalulw 4y ago
    To be fair, I'm not sure if you can demodulate a 100MHz FM signal digitally. DSP at this frequency on an Arduino maybe be infeasible (you need a phase locked loop). I suppose if you used a bandpass + low pass filter you can pull it off but that will be a lot more work still.
- 9wzYQbTYsAIc 4y ago
  The enclosure design was interesting - not 3d printed, unfortunately, but still looks remarkably clean. And the choice of user interface was interesting to see - a single rotary encoder reminiscent of the days of the iPod. But, yes, definitely more about how to wire together (physically and digitally) the components of a consumer product than about how FM radio chips work or how to build your own radio from crystals, etc.
  - daniel-cussen 4y ago
zython 4y ago
and for my next trick I'm going to make a slingshot with only two parts: a slingshot and a squirrel
- 9wzYQbTYsAIc 4y ago
  Hah, neat trick! https://allanimalsfaq.com/squirrel/how-to-make-a-squirrel-slingshot/ https://allanimalsfaq.com/squirrel/how-to-make-a-squirrel-sl...
gregsadetsky 4y ago
Would anyone be able to recommend the most beginner friendly “assume (almost) no knowledge” of how to implement an fm radio using 1) a dsp “pipeline” 2) analog electronics? If I wanted to understand every single step of the dsp process and what each individual piece of electronics did in “decoding” a fm signal, where should I turn to? Thank you!
- jrockway 4y ago
  FM radio receivers were a staple of those electronic kits I used to play with as a kid. Here's what a quick Google search shows: https://www.electronicsforu.com/electronics-projects/simple-fm-receiver https://www.electronicsforu.com/electronics-projects/simple-... The difference in complexity between this and something commercial are extras like decoding the stereo subcarrier and applying the data to the main signal: https://en.wikipedia.org/wiki/FM_broadcasting#Stereo_FM https://en.wikipedia.org/wiki/FM_broadcasting#Stereo_FM
  - gregsadetsky 4y ago
    Yeah, I also did electronic kits as a kid, and both learned how to read a diagram thanks to them, but never understood what individual parts did in any circuit. I “get” I=V/R (I mean not really… I know it exists), but how to go from there to understanding what each capacitor is doing in the simplest of fm circuits? Is each component doing the equivalent of non-trivial real-time signal processing? How to visualize / think about it?
- teeray 4y ago
  I’ve mentioned this on another sibling comment, but amateur radio is where you need to look. It took me about 6 months of casual study to go through all three license classes (tech took me like 2 weeks), and you learn quite a bit about everything you’ve mentioned in the process. More than that, you gain a license which allows you to legally experiment with this stuff.
thakoppno 4y ago
People in the US who find this interesting should spend the ~$50 to get licensed for amateur and buy a UV5R radio. There is just so much one can do and learn with these cheap radios. In many ways, it’s the raspberry pi of radio.
- Baeocystin 4y ago
  I've heard secondhand mutterings that the amateur radio doesn't like the Baofeng radios due to stomping over other frequencies when in use. Is this just expected internet kvetching, or is there more to it than that? I am interested in learning more, but I don't feel like running in to any more hostility in my hobbies. Genuine question.
  - thakoppno 4y ago
    It seems like that concern may have been addressed with the more recent releases of this model of radio since March of 2021. I certainly haven’t experienced spurious emissions first hand. I own a proper Yaesu radio now but the Baofeng is such a value imho for beginners to learn the hobby. One can talk to astronauts on the international space station with one.
  - BuildTheRobots 4y ago
    They tend to have relatively cheap front ends so put out more harmonic noise when broadcasting. They also tend to be direct conversion rather than superhet, meaning they can be more prone to interference on receive when you have a few of them together. If you're wanting to get into modern ham radio, then something like an Anytone 878 will do all the analogue as well as digital, which can be fun.
reaperducer 4y ago
An old WWII veteran who built the on-board CCTV system on a ship in the Pacific once walked me through making an AM radio that worked with no battery — just the power of the radio waves, themselves. Like what today powers RFID chips. It took him maybe ten minutes of soldering probably six or eight components he pulled out of a box of junk parts. He grounded the thing by sticking a nail into a wall socket. It helped that this was in a small town with only a couple of AM signals, so fine-tuning wasn't all that necessary.
- 9wzYQbTYsAIc 4y ago
  You might get a kick out of this: “I bought 1000 meters of wire to settle a physics debate” https://m.youtube.com/watch?v=2Vrhk5OjBP8 https://m.youtube.com/watch?v=2Vrhk5OjBP8
- password4321 4y ago
  AM: https://en.wikipedia.org/wiki/Foxhole_radio https://en.wikipedia.org/wiki/Foxhole_radio
- myself248 4y ago
  A crystal-set radio was a LOT of people's introduction to electronics, I remember building one with my dad at age 6 or so. We were a fair distance from the station so the signal was faint, but the earphone reproduced enough to hear the news and most importantly, the station call letters. They really are extremely simple things, and you can use the base-emitter structure in any BJT if you don't have a discrete diode around. The trick is knowing how many turns of wire to put on the inductor, but if you're stuck in a foxhole for who-knows-how-long, you have time for a lot of trial and error.
THENATHE 4y ago
In 1930-something, my grandfather built a passive radio to use on his family farmhouse without electricity. He ran a wire all the way from the basement (where he happened to get the best signal and for other reasons) all the way to his attic room, and would stay up late all night listening to the radio with his brother. An aside, but this article made me think of this fun little story.
- deevious 4y ago
  The wire from the basement was for an earth ground, he probably had another antenna wire either in the attic or going outside. Check out Galena detector radios.
- bdcravens 4y ago
  Yes, my grandfather did the same thing (a bit earlier, probably late 1910s or early 20s, as he was born in 1908). He used a cyclindrical oatmeal box and wound copper around it to make a tuner. The story was immortalized in a book the Texas Governor's Committee on Again published in the 70s. https://www.amazon.com/Texas-Sampler-Donna-Bearden-Frucht/dp/B004Q1GF58 https://www.amazon.com/Texas-Sampler-Donna-Bearden-Frucht/dp...
lloydatkinson 4y ago
84MHz? ARM? Talk about over engineering. As the FM receiver IC in this project uses I2C you could do this with an AVR even, such as the 328P, as found in the Arduino Nano. The Arduino Due used here is double the price of the Nano.
lormayna 4y ago
You can also make a shortwave receiver in a similar way with a SI473x chip. It's a bit more expensive, but it can demodulate also SSB.
djmips 4y ago
Original version mentioned in this blog/video. https://www.changpuak.ch/electronics/Arduino-Shield-WACHARA1.php https://www.changpuak.ch/electronics/Arduino-Shield-WACHARA1...

69 points by 9wzYQbTYsAIc 4y ago

> Building an FM radio from $3 radio chip and an 84MHz ARM Arduino The article is great. He just forgot to explain how and why (84 Mhz microcontroller for a FM radio ? ) he did it. /s

9wzYQbTYsAIc 4y ago
Another day, another hack, is the hackaday way.
squarefoot 4y ago
That in fact is quite overkill; probably it was what he had at hand. That FM chip can be controlled by any uC capable of bitbanging i2c, so pretty much every cheap one including small ATTiny uCs that cost one tenth of the Arduino Due.

anaganisk 4y ago

Didn’t RPI have In built capability to do that? I built a cheap streaming system, back when bluetooth wasn’t so main stream to make “piplay” for my stereo in car with Pi2.

9wzYQbTYsAIc 4y ago
I’m not sure, it might. As I recall, some ARM SoC have FM radios in them. edit: ah, it was the Qualcomm modems that I was recalling https://www.wired.com/2016/07/phones-fm-chips-radio-smartphone/ https://www.wired.com/2016/07/phones-fm-chips-radio-smartpho...
bdowling 4y ago
Sort of. The Raspberry Pi CPU had a configurable clock generator that could output up to about 125MHz to a GPIO line. Some people figured out that it was possible to rapidly change the configuration registers to modulate an audio signal onto a carrier frequency in the FM broadcast range. [0] So you could make a low power FM transmitter using just a Raspberry Pi and a piece of wire. [0] http://www.icrobotics.co.uk/wiki/index.php/Turning_the_Raspberry_Pi_Into_an_FM_Transmitter http://www.icrobotics.co.uk/wiki/index.php/Turning_the_Raspb...

deleted 4y ago

[deleted]

amelius 4y ago

... based on the TEA5767 radio module. So this is more a lesson in how to wire things together than it is in how FM radio even works.

teeray 4y ago
The TEA5767 is a full FM broadcast receiver on a chip. So yeah, it’s really just how to wire up that chip, connect it to an audio amplifier (LM4811), etc. If you want to learn how radios work, I’d recommend many of the learning materials out there for amateur radio.
- omegalulw 4y ago
  To be fair, I'm not sure if you can demodulate a 100MHz FM signal digitally. DSP at this frequency on an Arduino maybe be infeasible (you need a phase locked loop). I suppose if you used a bandpass + low pass filter you can pull it off but that will be a lot more work still.
9wzYQbTYsAIc 4y ago
The enclosure design was interesting - not 3d printed, unfortunately, but still looks remarkably clean. And the choice of user interface was interesting to see - a single rotary encoder reminiscent of the days of the iPod. But, yes, definitely more about how to wire together (physically and digitally) the components of a consumer product than about how FM radio chips work or how to build your own radio from crystals, etc.
- daniel-cussen 4y ago

zython 4y ago

and for my next trick I'm going to make a slingshot with only two parts: a slingshot and a squirrel

9wzYQbTYsAIc 4y ago
Hah, neat trick! https://allanimalsfaq.com/squirrel/how-to-make-a-squirrel-slingshot/ https://allanimalsfaq.com/squirrel/how-to-make-a-squirrel-sl...

gregsadetsky 4y ago

Would anyone be able to recommend the most beginner friendly “assume (almost) no knowledge” of how to implement an fm radio using 1) a dsp “pipeline” 2) analog electronics? If I wanted to understand every single step of the dsp process and what each individual piece of electronics did in “decoding” a fm signal, where should I turn to? Thank you!

jrockway 4y ago
FM radio receivers were a staple of those electronic kits I used to play with as a kid. Here's what a quick Google search shows: https://www.electronicsforu.com/electronics-projects/simple-fm-receiver https://www.electronicsforu.com/electronics-projects/simple-... The difference in complexity between this and something commercial are extras like decoding the stereo subcarrier and applying the data to the main signal: https://en.wikipedia.org/wiki/FM_broadcasting#Stereo_FM https://en.wikipedia.org/wiki/FM_broadcasting#Stereo_FM
- gregsadetsky 4y ago
  Yeah, I also did electronic kits as a kid, and both learned how to read a diagram thanks to them, but never understood what individual parts did in any circuit. I “get” I=V/R (I mean not really… I know it exists), but how to go from there to understanding what each capacitor is doing in the simplest of fm circuits? Is each component doing the equivalent of non-trivial real-time signal processing? How to visualize / think about it?
teeray 4y ago
I’ve mentioned this on another sibling comment, but amateur radio is where you need to look. It took me about 6 months of casual study to go through all three license classes (tech took me like 2 weeks), and you learn quite a bit about everything you’ve mentioned in the process. More than that, you gain a license which allows you to legally experiment with this stuff.

thakoppno 4y ago

People in the US who find this interesting should spend the ~$50 to get licensed for amateur and buy a UV5R radio. There is just so much one can do and learn with these cheap radios. In many ways, it’s the raspberry pi of radio.

Baeocystin 4y ago
I've heard secondhand mutterings that the amateur radio doesn't like the Baofeng radios due to stomping over other frequencies when in use. Is this just expected internet kvetching, or is there more to it than that? I am interested in learning more, but I don't feel like running in to any more hostility in my hobbies. Genuine question.
- thakoppno 4y ago
  It seems like that concern may have been addressed with the more recent releases of this model of radio since March of 2021. I certainly haven’t experienced spurious emissions first hand. I own a proper Yaesu radio now but the Baofeng is such a value imho for beginners to learn the hobby. One can talk to astronauts on the international space station with one.
- BuildTheRobots 4y ago
  They tend to have relatively cheap front ends so put out more harmonic noise when broadcasting. They also tend to be direct conversion rather than superhet, meaning they can be more prone to interference on receive when you have a few of them together. If you're wanting to get into modern ham radio, then something like an Anytone 878 will do all the analogue as well as digital, which can be fun.

reaperducer 4y ago

An old WWII veteran who built the on-board CCTV system on a ship in the Pacific once walked me through making an AM radio that worked with no battery — just the power of the radio waves, themselves. Like what today powers RFID chips. It took him maybe ten minutes of soldering probably six or eight components he pulled out of a box of junk parts. He grounded the thing by sticking a nail into a wall socket. It helped that this was in a small town with only a couple of AM signals, so fine-tuning wasn't all that necessary.

9wzYQbTYsAIc 4y ago
You might get a kick out of this: “I bought 1000 meters of wire to settle a physics debate” https://m.youtube.com/watch?v=2Vrhk5OjBP8 https://m.youtube.com/watch?v=2Vrhk5OjBP8
password4321 4y ago
AM: https://en.wikipedia.org/wiki/Foxhole_radio https://en.wikipedia.org/wiki/Foxhole_radio
myself248 4y ago
A crystal-set radio was a LOT of people's introduction to electronics, I remember building one with my dad at age 6 or so. We were a fair distance from the station so the signal was faint, but the earphone reproduced enough to hear the news and most importantly, the station call letters. They really are extremely simple things, and you can use the base-emitter structure in any BJT if you don't have a discrete diode around. The trick is knowing how many turns of wire to put on the inductor, but if you're stuck in a foxhole for who-knows-how-long, you have time for a lot of trial and error.

THENATHE 4y ago

In 1930-something, my grandfather built a passive radio to use on his family farmhouse without electricity. He ran a wire all the way from the basement (where he happened to get the best signal and for other reasons) all the way to his attic room, and would stay up late all night listening to the radio with his brother. An aside, but this article made me think of this fun little story.

deevious 4y ago
The wire from the basement was for an earth ground, he probably had another antenna wire either in the attic or going outside. Check out Galena detector radios.
bdcravens 4y ago
Yes, my grandfather did the same thing (a bit earlier, probably late 1910s or early 20s, as he was born in 1908). He used a cyclindrical oatmeal box and wound copper around it to make a tuner. The story was immortalized in a book the Texas Governor's Committee on Again published in the 70s. https://www.amazon.com/Texas-Sampler-Donna-Bearden-Frucht/dp/B004Q1GF58 https://www.amazon.com/Texas-Sampler-Donna-Bearden-Frucht/dp...

lloydatkinson 4y ago

84MHz? ARM? Talk about over engineering. As the FM receiver IC in this project uses I2C you could do this with an AVR even, such as the 328P, as found in the Arduino Nano. The Arduino Due used here is double the price of the Nano.

lormayna 4y ago

You can also make a shortwave receiver in a similar way with a SI473x chip. It's a bit more expensive, but it can demodulate also SSB.

djmips 4y ago

Original version mentioned in this blog/video. https://www.changpuak.ch/electronics/Arduino-Shield-WACHARA1.php https://www.changpuak.ch/electronics/Arduino-Shield-WACHARA1...