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Topic: Si4737 I2C Arduino Radio Breakout (Read 2 times) previous topic - next topic


Jun 03, 2013, 04:26 am Last Edit: Jun 03, 2013, 04:30 am by Alex_K Reason: 1
I have designed breakout board for Arduino Radio based on Si4737, it's similar to Si4735 breakout but improved and using I2C. I am sure it's 101% functional but I am having difficulty to get it running, I modified two Arduino libraries of Si4735 to be compatible with my breakout and even tried to write my own code without library to power up and tune to station but having exactly the same issue:
Radio power-up command works but it won't tune, status request from Si4737 is 0x80 (clear to send) and everything seems normal except it won't tune.
When I send power-up  command I hear small pop in speakers and I can read 0x80, seek to station won't work or auto seek, and no sound. Please help to get it running I got 40 of them and can't make it work, spend days to figure out, I know it's something simple, just can't find it.

To the first person that helps me solve this I will mail one of my Radio breakout boards for free as a appreciation.
Actual circuit and board shown below



so questions :  sorry if this is spoon feeding, just trying to judge the level.

   Are you familiar with Rf signal lay out and requirements ?
      do you have a scope and a spectrum analiser,

do you have one of the evaluation boards

do you have AN332


I am not a genius in RF signal requirements or magnetics, but I do know enough to make FSK data transmitters and receivers. Overall I am really good at hardware design, I designed and build 1GHz ARM Linux boards and everything works as expected. When I look at Sparkfun Si4735 radio shield I realize that they design board ignoring RF requirements, amperage, voltage, not calculating component values, making bad copy of a component datasheet circuit.

Does it really matter if I have oscilloscope or not? At a moment NO, but I do have professional testing and re-flow equipment. My old oscilloscope died recently and didn't had a spare money to get a good one, I do know what it is and how to use it.

No, I don't buy 100+ dollar development board because it's not worth it, it's cheaper to get PDF and make one yourself if I need.

Yes, I read AN332 and understand how to send and receive commands, I am not a great programmer but I can definitely make communication code with whatever I am interfacing with.

I need to understand why radio will respond to power-up command and I tried changing volume settings and it works, I checked by getting register status, but why on earth it won't tune? When I set frequency and read back current tuned frequency it responds with 0.

Is on-board antenna trace too small? Is radio not setting frequency that I specified if there is a poor signal? Anybody had any similar experience with Si47xx series of radio chips? It just drives me nuts.



As I implied, sorry needed to know what level to start, If I'd started to talk VSWR to a student on their first project, it would not have helped.

Ok, so :

comms. If I rember, the chip has a revision register, does that read back just fine ?
      the question about the scope is because spikes on the comms lines from the closely coupled radio can cause mayhem to comms, what seems to be working at the terminal just does not get to the chip corectly.

The question about the app note was simply , its amazing how many people dont use the app notes. Well done.

Re the eval board, you see my time is worth a few dollars per hour. So a hundred for a known working demo board on which i can dev the software is to me a good bet. allows us to dev the software before I get boards back. just a suggestion. The problem you now have is , is it thee software, the compiler, the connections, the board or the understanding of how the chip works.

If you had a known good to work from then things might be easier.


Well, you are right, but even if I had a functional example it would ran of different MCU and programming environment. I need to make it run of Arduino programming environment with any of Atmel MCU's and I know nothing is wrong electronically with the board itself. I tested board again by attaching long wire for FM antenna to get better signal reception and get the same result. I will try to read revision register to see what happens.

Maybe it doesn't work because I don't have an oscilloscope.  :D
I have to order one and see what happens.

Thank you for trying to help me.

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