Interesting Chinesium SI4732 Shortwave/Air/FM

[syfr]

I'll be watching your progress.  A software "kit" is a good way to look at it.   

Please keep posting what you find, it's much appreciated.

[RobRich]

Thanks and will do. :)

Copy-and-paste about the latest firmware update:

* The final code (HEX file) is about 2.5K smaller than the previous one (now you have more memory to add new features);
* Twenty three bands. Two VHF(FM); one LW; two MW; and Nineteen SW bands covering from 1800 to 30000 kHz;
* Band, Volume, Step, Bandwidth, AGC/Attenuation are now controlled by encoder;
* "Vol-" buttons is free to implement new features. It has no function for while;
* "BAND-" now is used to control Softmute Attenuation;
* All the previous status of the receiver can be rescued when you turn it on (including SSB mode, bandwidth, volume, frequency, BFO etc);
* The bandwidth now is a property of the band (you can use different bandwidth for different bands);
* Bandwidth control on FM mode (Auto, 110, 84, 60 and 40 kHz);
* Bandwidth control on AM mode (1, 2, 2.5, 3, 4 and 6 kHz);
* Bandwidth control on SSB mode (0.5, 1, 1.2, 2.2, 3 and 4 kHz);
* AGC (Automatic Gain Control) and Attenuation control;
* Softmute Attenuation Control;
* FM/RDS presentation was improved;
* The seek function was improved (it is more precise on FM mode). The seek direction is controlled by the encoder (clockwise or counter-clockwise. Press encoder push button for seeking Steps: 1, 5, 9, 10, 50 and 100 kHz;
* Now you can configure MW band space to 9 or 10 kHz;
* New FM band from 64 to 84 MHz;
* New MW band from 531 to 1701 kHz for Europe, Africa and Asia;
* The frequency on Display is bigger than the previous version;
* Now the bandwidth sequence is ordered by bandwidth values;
* After about 4 seconds, all command buttons are all disabled and the encoder control goes back to the frequency;
* The current status of the receiver will be stored only after 10 seconds of inactivity.

[syfr]

That's cool, and a lot of changes. Are they managing the changes through Git or something similar?

I'm pretty sure you must be better at working with downloading/building firmware than I am .   :-)

[RobRich]

PU2CLR maintains a git repository for SI47xx software:

https://github.com/pu2clr/SI4735

The specific firmware I am using:

https://github.com/pu2clr/SI4735/tree/master/examples/SI47XX_KITS/AliExpress

There also are groups for the SI47xx chip in general:

https://www.facebook.com/groups/532613604253401/
https://groups.io/g/si47xx/topics

I poke at and build* software casually, but I am not really into the Arduino stuff, so I had to install the IDE.

I was just following the directions. Thankfully no command lines, git commands, or complicated steps. The IDE itself pulls in all the needed parts from an Internet database. Basically search, install three libraries, click a few options, then upload to the radio. If anyone does it, definitely remember to hold in the encoder while powering the radio to reset the EEPROM after the firmware upgrade.

I did glance at the source. It is well laid out and commented if one wanted to change things such as button assignments or whatever.

*One of my other hobbies is optimizing and building the Chromium web browser.

https://chromium.woolyss.com/

[RobRich]

For the more adventurous, apparently a dev even has added a CW decoder to his firmware.

http://www.cqham.ru/forum/showthread.php?33038-Elektor-DSP-Radio-%ED%E0-%F7%E8%EF%E5-Si4735&p=1828648&viewfull=1#post1828648

I am somewhat surprised it fit. The Arduino Nano - well, it is a clone here to be technical  - only has like 30KB of usable memory.

[syfr]

Thanks for the good info. I can use the IDE ok, and I'm good at following the bouncing ball instruction-wise, but it doesn't take much to happen to put me out into the weeds.  I'm one of those eternally grateful for installation packages.

Yeah, there's not a lot of extra headroom in a Nano, so it's cool they got a decoder packed in there. I've never seen one work very well under real world conditions, but it's fun to play with them.

Cool toy for small bucks it seems like.

[RobRich]

I have one these....

https://mfjenterprises.com/products/vec-162

....on a shelf collecting dust. Been there for years. It might be better for RTTY and whatever, but yeah, I agree CW can be quite a YMMV situation in my experience.

[RobRich]

I have uploaded several photos of the receiver internals:

https://imgur.com/a/Gl3MLGA

[RobRich]

Antenna path closeup:

https://imgur.com/a/8ODg9YB

Caps are there, so at least the antenna jack is not straight to the chip. Still, no matching inductors or ESD protection.

I am not too concerned about the inductors, as I am not trying to match the included whip antenna.

I expected the lack of ESD protection, as IIRC, the chip SI recommends is like ~$1 a piece.

[RobRich]

I did not spend much time delving into the design. I just went with the quick-and-dirty approach of throwing parts at it. ;)

https://imgur.com/a/Tn7VvpR

Those are 47uF electrolytics and .1uF ceramics on the Arduino Nano (clone) power rails.

Crossed 1N4148 diodes and a 1M carbon resistor at the BNC connector.

BTW, yeah, my soldering "skills" are horrid. I do good to type sometimes; less long solder anymore.

[syfr]

Hey, if it works, and is reliable, it's all great once you button up the case.   It looks good to me.

Hopefully that'll serve to lower some of the noise on the 5V rail. Nice work!

[RobRich]

Thanks. The receiver still works, so at least that is something. ;)

IIRC, all the power pins - except the USB port of course - at the Arduino Nano clone read around 3.x volts. I suspect the control board and Si chip are being run at ~3.3v operation.

The Si4732 is rated down to 2.7v, and apparently the Nano's controller can go down to 3.3v or perhaps lower without much issue, especially if it is not being pushed hard.

[syfr]

Hardware hackery that still allows an assembly to work after the soldering iron has cooled, goes into the + category. It's SO easy to wound these things.  Good work on keeping the smoke inside!

[RobRich]

I could have tried adding similar filtering at the USB port or voltage regulator(s), but I left those alone for now due to soldering on smaller pins plus not wanting to accidentally disturb the ability to USB flash firmware. I know a random USB charger was rather noisy on MW+HF as expected. I have been using it on battery power, though no real idea on runtime as I have been charging it between uses instead of letting it run down.

I have thought about looking into a speaker replacement as it seems rather narrow. "Okay" for talk and voice comms. Not so great for music, though admittedly that might be more a function of the audio circuit than the speaker. Suppose I should get around to hearing how it sounds with headphones to get a better idea.

[syfr]

Article and FB (ughhh) group re: new software for this thing:

https://swling.com/blog/2021/05/si473x-receiver-firmware-update-and-internal-photos/?utm_source=feedburner&utm_medium=email&utm_campaign=Feed%3A+TheSwlingPost+%28The+SWLing+Post%29