Rogers postbag - FM radio band transmitter

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raphik
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Re: Rogers postbag - FM radio band transmitter

Postby raphik » Sun Feb 19, 2017 4:44 am

@RogerClark
I soldered a pair of wires to a couple of spare GPIOs on the board. Those GPIO were thought for a pair of LEDs that the builder never put on the board.
Image
Then I took the wires out and connected them to an I2C expansor.
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For the software, under Linux, it is first necessary to identify what GPIOs you are using, in order to export and declare them as outputs. The package kmod-i2c-gpio-custom has then to be installed. After that, the I2C bus can be mounted. Reboot the router and the bus is ready for its usage.

You can find detailed, translated instructions here -> https://translate.google.com/translate?sl=es&tl=en&js=y&prev=_t&hl=es&ie=UTF-8&u=http%3A%2F%2Fforo.seguridadwireless.net%2Fopenwrt%2Fproyecto-gpio-manejo-de-una-pantalla-lcd-via-bus-i2c%2F&edit-text=

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RogerClark
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Re: Rogers postbag - FM radio band transmitter

Postby RogerClark » Sun Feb 19, 2017 9:56 am

Thanks for the explanation. I didnt realise it was possible to get Linux to operate I2C via 2 GPIO pins

Connecting to unused LED's is also a good idea. I presumed that these routers would not have GPIO but of course they must have it as they have LED's and often have buttons (switches) as well

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ahull
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Re: Rogers postbag - FM radio band transmitter

Postby ahull » Sun Feb 19, 2017 10:53 am

You can use a broadly similar method to get i2c on the Pi -> https://learn.adafruit.com/adafruits-ra ... guring-i2c
Accessing the i2c eerom on those FM transmitter boards might be easier with a suitable clip on adapter.
Search ebay for "SOIC8 SOP8 Flash Chip IC Test Clips Socket Adpter BIOS/24/25/93 Programmer"
Image
I used one of these to hack the 24c02 on a couple of VC921 multimeters with a bluepill (details elsewhere on stm32duino.com)
- Andy Hull -

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BennehBoy
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Re: Rogers postbag - FM radio band transmitter

Postby BennehBoy » Sun Feb 19, 2017 11:22 am

Very interesting, I have a spare WRT54G sat in the cupboard which has openwrt installed....

Looks like I can hack SPI into mine :D

https://wiki.openwrt.org/toh/linksys/wrt54g
-------------------------------------
https://github.com/BennehBoy

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RogerClark
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Re: Rogers postbag - FM radio band transmitter

Postby RogerClark » Sun Feb 19, 2017 8:58 pm

ahull wrote:Accessing the i2c eerom on those FM transmitter boards might be easier with a suitable clip on adapter.
Search ebay for "SOIC8 SOP8 Flash Chip IC Test Clips Socket Adpter BIOS/24/25/93 Programmer"
Image
I used one of these to hack the 24c02 on a couple of VC921 multimeters with a bluepill (details elsewhere on stm32duino.com)


Thanks Andy

I think I should buy a few different types / sizes of these.

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zoomx
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Re: Rogers postbag - FM radio band transmitter

Postby zoomx » Tue Feb 21, 2017 7:30 am

RogerClark wrote:PS. I see a youtube video about building an internet radio using a wireless router, and I have a spare ASUS router which I could install OpenWRT onto (I know it works with DDWRT), but I think thats another project I'll need to add to the list of things to do when I have more free time.


I made it with a wireless router and an USB audio dongle. Only tested but it works. I used some apps on Android and on PC to have control.

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Vassilis
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Re: Rogers postbag - FM radio band transmitter

Postby Vassilis » Tue Feb 21, 2017 2:07 pm

@Roger
Has the FM transmitter you purchased good sound quality (clear sound) ?

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RogerClark
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Re: Rogers postbag - FM radio band transmitter

Postby RogerClark » Tue Feb 21, 2017 8:16 pm

Vassilis wrote:@Roger
Has the FM transmitter you purchased good sound quality (clear sound) ?


Yes. The one you posted the link to, works well.

Audio is very clear. I get a very small amonut of hiss but I think that comes from the bluetooth audio receiver.

The transmission seems to be quite narrow band as well, and does not cause interferance on adjacent frequencies.

raphik
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Bare but ready-to-use FM radio band transmitter

Postby raphik » Wed Feb 22, 2017 11:57 am

I would like to link this FM transmitter module to my next-to-be-bought STM32 MCU through its i2c bus. But having the 8027 IC SDA and SCL pins welded to its original board is a bit annoying because of the interferences with onboard "JL MCU". So one can think buying a bare QN8027 could be a good idea. But a bare QN8027 is difficult to handle. And what is more, without a bunch of extra electronics it doesn't really make an FM transmitter.
Image

Perhaps it's a better idea to buy a ready-mounted one like this:
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(Seen here http://www.taobaofrench.com/p-18489373313.html)

The get QN8027 properly working is necessary to know the initialization sequence (found here: http://share.dzkf.cn/down/search.php?ke ... D1+%CB%F7+)

Summarizing:
Step1: Write QN8027 Reg0x00=0x81; // Reset all registers to the default value
Step2: Delay 20ms
Step3: Write QN8027 Reg0x03=0x50; //set external clock
Step4: Write QN8027 Reg0x04=0x33; //set 12MHz clock
Step5: Write QN8027 Reg0x00=0x41; //FSM calibrate
Step6: Write QN8027 Reg0x00=0x01; //FSM calibrate complete
Step7: Delay 20ms
Step8: Write QN8027 Reg0x18=0xE4; //Improve SNR
Step9: Write QN8027 Reg0x1B=0xF0; //Increase RF power output maximum
Step10: Write QN8027 Reg0x01=0x7E; //set channel
Step11: Write QN8027 Reg0x02=0xB9; //disable RF PA off function
Step12: Write QN8027 Reg0x00=0x22; //transmitting

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Vassilis
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Re: Rogers postbag - FM radio band transmitter

Postby Vassilis » Wed Feb 22, 2017 1:06 pm

The arduino QN8027 library is also interesting for learning the QN8027 registers.


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