SparkFun Forums

[roach]

I'm thinking of including an FM receiver function in a little MP3 player project I'm working on. Can anyone recommend a simple, cheap IC that would be good for this? Ideally I'm looking for something that requires a minimum of external components, and can be digitally tuned (ie: frequency tuning using a digital IO from the uC). Any ideas?

[busonerd]

Phillips makes a nice one... its really really heavily NDA'ed though. But its about the simplest I've seen.

Samsung also makes one.. looks to be more complex to interface, but should work.

--David Carne

[riden]

Around our parts we have Dollar Stores (where everything is priced at $1). They sell an FM receiver and integrated LED flashlight for, well, a dollar. It has really great sensitivity and you set the frequency using Up and Down switches. Not direct frequency synthesis, but you might be able to lift the parts off the board and have your processor tickle the up/dn switches. It might we worth looking into if you can find them locally.

This link isn't where I bought mine, but it shows you what it looks like.

[roach]

Riden: That looks pretty sweet, and might work. Thanks! The only problem is that this project has an LCD screen, where I was hoping to display the current frequency to the user. If I could digitally tune the receiver, then I would always have that feedback of the current frequency. If I "tickle" the up/down controls as you suggest, I'll never really "know" the current receiver frequency. I can't tell if there's some sort of diaply of the current frequency on that thing. If there is, I could maybe tap into that...

[busonerd]

I've seen something similar - however.. its all analog. It charges a cap to drive a VCO, IIRC.

--David Carne

[riden]

I'll have to take a closer look at the board to see if it charges a cap like David said or if it goes directly into the chip.

This suggestion is a bit of a hack, but you could reset the receiver which brings it to 88.7? Mhz and then have the processor count up to the desired freq. Once that is established and the receiver and processor are synced, the controller can bump the freq and update the display as well. This approach may be unworkable however if you need to wait a short period between presses. Anyhow, I'll have a look tonight to satisfy my curiousity.

[tctan2001]

Take a look at this FM tuner. Super simple to use with minimum external components.

Too bad I still cannot find the source for small quantity. Mouser has them on backordered with no date for time of arrival.

http://www.silabs.com/tgwWebApp/public/ ... 700-01.htm

[Philba]

how is SiLabs when it comes to samples?

[riden]

I'll have to take a closer look at the board to see if it charges a cap like David said or if it goes directly into the chip.
... I'll have a look tonight to satisfy my curiousity.

I had a look at the $1 FM receiver, and although I didn't spend a lot of time, I can tell you a little more about it...

-- Runs at 3v (powered by two AAA cells)
-- The receiver chip is an unknown 16 pin SOIC part (manufacture's markings were removed)
-- Two pushbutton switches going INTO the chip, Reset and Scan (step)
-- Each press of the Scan button goes to the next FM channel
-- No variable capacitor but there is a diode which could be a varactor
-- The flashlight is not an LED but an incandescent lamp

Probably not the best choice for your purposes, but it is an interesting curiousity anyway.