Comments on: RF Data Link Using Si4021 And Si4311

By: kwong

kwong — Wed, 16 May 2012 01:23:49 +0000

Hi Chris, I don’t believe the value of the 22nF bypassing capacitor is that critical. But if you are using a larger capacitor, it probably would be helpful to put a smaller value one in parallel for better bypassing. Using a simple antenna, I had no problem of reaching 100 feet with a Si4311 transmitter (power set to max) in open space.

By: Chris T

Chris T — Tue, 15 May 2012 07:54:10 +0000

Hi Kerry,

thanks a lot for your quick response. This seems like the only place in the web, where experience with the 4311 is shared. I made a new board yesterday with jumpers for configuration. However, I didn’t find a setting, that improves the range. The signal qualtity seems more stable. Maybe it’s not changing over time anymore, but is only a function of distance. The range is still bad. My question this time is, could it be related to a different thing than the setting. Here are the specs: I am running driectly from a lipo, so the supply voltage is around 4V. This is above the rating, but since they write there is a LDO inside, it should be ok. Second, The antenna is a wire directly connected to the pin, No L and C there. Also, I am using only a 4.7uF ceramic cap. Is the 22n so essential. I am doing all this with the 4320 as well, and it works fine (on 915MHz) I have been flying models with this setup for a while, reliable radio link. Maybe there is a difference in the design of the 4311 and it is reacting differently to changes of the recommended setup. Any input is welcome. I am really interested what range you got. Would you please let me know?

Thanks again.

Chris

By: kwong

kwong — Mon, 14 May 2012 17:10:17 +0000

Hi Chris,

It has been a while…. if I remember correctly, you might need to adjust pin 14 and pin 15 settings depending on the bit rate you are using. Other than that, I don’t recall having an issue with the receiver performance.

By: Chris T

Chris T — Mon, 14 May 2012 14:49:00 +0000

Hi, I am using the exact same chips for a radio link. I have quite some experience with the SI4320 rx and moved to the SI4311 due to its small size. I am running both receivers in parallel for comparison and see some strange behavior on the SI4311. First the radio link is established, after a while it seems to loose the signal, I see some errors in the signal sometimes it is gone completely and all of a sudden it shows up inverted. I asume the afc is scanning for the optimium frequency and is going crazy, maybe pushing one tone out of band. Either my input signal is not to spec, but I tried to detune in both directions and didn’t find a better operating point. Or, some settings on the 4311 need to be changed. I will make a new board to fool around with the afc bw and deviation pins. The 4320 has the afc activated as well and there it is working well. I need about 100 meters of save range for a model airplane. I am using a printed loop antenna on the tx and just a wire on the rx pin without the LC. The LC should only be required for 50Ohm impedance matching. A lambda/4 dipole antenna should connect directly, correct? I am doing this on the 4320 as well and have good range. With the 4311 I get into trouble at 5 meters already. Any ideas? Any experience with range? Thanks a lot for the help. Maybe a smaller deviation, deactivated afc with manually tuned tx and probably one step lower bw might do it. I will try.

Cheers,

Chris

By: kwong

kwong — Wed, 01 Feb 2012 15:39:13 +0000

Sure thing. You read from the receiver output as you would from an UART output. So if you are testing this with an Arduino, you can simply connect the output from Si4311 to the Rx pin on ATmega328 and use Serial Monitor to see the received data (you will have to set the baud rate to be the same as the transmitter side).

By: Abhay

Abhay — Wed, 01 Feb 2012 13:11:14 +0000

Hi Kerry,
Could you please explain me how to read data from Si4311 receiver?
Thanks,
Abhay

By: kwong

kwong — Tue, 23 Aug 2011 21:24:46 +0000

Hi John,

1) The output of SI4311 is UART compatible so you could use a UART-USB chip (e.g. FT232R) for this purpose.
2) BT0 BT1 DEV0 DEV1 are set according to datasheet. You can start from a low bit rate and set all of these pins to 0 to start with (it should work in this configuration). The settings mainly affect the bit time and frequency deviation and thus affect the range.

By: John

John — Tue, 23 Aug 2011 18:59:19 +0000

Hi Kerry!
1) Do you try to connect SI4311 output directly to USB-UART dongle and observe signals on terminal?
2) How do you configured BT0 , BT1 and DEV0, DEV1 pins?

By: Lee

Lee — Thu, 04 Aug 2011 16:25:08 +0000

I want to wirelessly monitor two devices that are not easily accessible. If one continues to function and the other goes off-line, it makes a mess. The office I want to monitor them from is not far from the devices. I have worked out how to interface the devices so that when they are operating, they will cause the RF transmitter to come on. Can someone help me design a monitor that would receive the 2 RF signals, interface their output to an AND gate and sound a buzzer if either device goes off-line. Please be patient. I can make PCB’s and solder well, but not a strong designer. I only need a schematic and brief explanation.

Thanks for your help

By: Mike Cook

Mike Cook — Tue, 07 Jun 2011 19:02:52 +0000

Never mind… Just read the 4311 spec sheet. It’s basically hardwired for this specific frequency. I was looking at the 4320 earlier. And that chip was software configurable for frequency.

Thanks,
Mike

By: Mike Cook

Mike Cook — Tue, 07 Jun 2011 15:02:35 +0000

Oops.. meant 916.68 MHz. Transposed my digits.

Mike

By: Mike Cook

Mike Cook — Tue, 07 Jun 2011 12:55:31 +0000

Hi,

Since last December, I’ve been using my hardwired serial interface which I connected to the FSK input on the 4021 chip. That works fine. I continue to be able to pull data from the chip.

But, I figured I’d try to receive the data via Wireless. This would make it much easier for me. To that end, I figure I could do what you did in this experiment. Although in my case, I’d be receiving at 961.68 MHz.

I was wondering how you set the receive frequency on the 4311 chip. Your code simply reads data from the chip. Wouldn’t I need to set the receiving frequency? For example, it appears as if you are setting the transmitter frequency to 433.92 MHz. How does the receiver know to listen on this frequency?

Thank you,
Mike

By: kwong

kwong — Sun, 13 Feb 2011 00:13:02 +0000

I used the reference schematics from the datasheet.

By: CaeJae

CaeJae — Sat, 12 Feb 2011 15:51:38 +0000

Can you provide the schematics used in your project?

By: kwong

kwong — Wed, 29 Dec 2010 00:46:34 +0000

Glad you figured it out!