Rogers postbag - FM radio band transmitter

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RogerClark
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Re: Rogers postbag - FM radio band transmitter

Post by RogerClark » Sat Feb 18, 2017 9:37 pm

@rapjik

What MCU did you try attaching to the board.

You said in your Welcome post that you are not using the STM32, so I wonder if the problem was some sort of voltage level.

I have a feeling that this board runs on 3.3V.

BTW. Do you know what the pad labelled M is used for ?

Thats the only pad I dont understand. It seems to have 3.3V on it. So I suppose it could be a 3.3v output.
But I only measured it with a multimeter, not a scope, so its possible it could have data in it

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ahull
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Re: Rogers postbag - FM radio band transmitter

Post by ahull » Sat Feb 18, 2017 9:51 pm

From the pictures the mysterious pin "M" goes to pin 24 on the mystery 48 pin MCU, and since the adjacent pins drive the LCD (and are thus probably GPIO) I suspect it is an I/O pin of some sort.
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RogerClark
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Re: Rogers postbag - FM radio band transmitter

Post by RogerClark » Sat Feb 18, 2017 9:57 pm

Thanks Andy

I wonder if its some sort of Mode input. It has 3.3v on it.

I will try pulling it low, via a 1k resistor, and see what happens ;-)

PS.
Shame we dont know what the MCU is.

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Re: Rogers postbag - FM radio band transmitter

Post by RogerClark » Sat Feb 18, 2017 10:22 pm

Update.

I pulled the M pad low, and it only drew about 0.5mA, so I suspect it is an input, because if it was being driven high by the MCU a lot more current would be drawn when I connected my analogue multimeter straight across those pins

However, I don't see any change in the operation if I pull it low, not even if I pull it low and power cycle it.

I connected the Serial port, and also tried the same thing again, but nothing gets reported when I pull the pin low, either while power is on, or when holding it low during powerup

Edit.

I thought it could be an external Mute control, but pulling it low doesn't seem to effect the audio from the MCU (played via my PCs' USB)

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RogerClark
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Re: Rogers postbag - FM radio band transmitter

Post by RogerClark » Sat Feb 18, 2017 10:43 pm

I have figured out what I was doing wrong with the serial comms

The command set is not the same as listed on the "falconchristmas" site

Looking at what Raphik was sending. The commands actually contain the less than and greater than chars e.g.

Code: Select all

AT<RET>
returns

Code: Select all

/***********************************/
VOL=30
FRE=870
PLAY
BANK=20s
CAMPOS_OFF
LCD_FM_X_V2.1.6
Thank you for using!
/***********************************/
But I don't know the complete set of commands

Some commands listed elsewhere like AT<VOL>=20 don't work on this module

I wonder whats in the SPI EEPROM, possibly commands ?

Edit.
AT<CAMPUS> doesnt work either

and even if I try their spelling from above e CAMPOS

I presume there is a way to enable CAMPUS mode, but its going to be hard to figure out what that is

I've also tried AT<LIST> and AT<HELP> and AT<?> in case any of those would give me a list of valid commands but I don't get any response.

So it looks like all of these modules are different, and it would be impossible to tell which version you would receive if you ordered from eBay or AliExpress

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ahull
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Re: Rogers postbag - FM radio band transmitter

Post by ahull » Sat Feb 18, 2017 11:16 pm

Is this of any use -> http://www.kh-gps.de/fm_china_at.pdf BTW this PDF appears to be for a related receiver rather than transmitter.
Another receiver (note receiver not transmitter) here -> http://www.ebay.co.uk/itm/87-108MHz-Dig ... 2046005965
Last edited by ahull on Sat Feb 18, 2017 11:24 pm, edited 2 times in total.
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raphik
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Re: Rogers postbag - FM radio band transmitter

Post by raphik » Sat Feb 18, 2017 11:21 pm

@RogerClark
I am attaching the FM board to pair of GPIO pins of an AR-5287un router running a tiny version of Linux called OpenWRT. I have already successfully attached this router to a LCD board http://foro.seguridadwireless.net/openw ... a-bus-i2c/.
So I guess the problem is that both the router and the FM board are trying to access the I2C bus at the same time.

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RogerClark
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Re: Rogers postbag - FM radio band transmitter

Post by RogerClark » Sun Feb 19, 2017 12:01 am

Andy

I found the same thing. The commands in my board appear to be similar but not completely the same as that receiver module.

Some other places e.g. that Chistmas lights site, seem to have a different board, as they have a more standard command set without the <>

@Raphic

It seems odd that the MCU on the transmitter would be constantly sending data to the radio chip, but I'd not rule it out.

If I get time later I'll hook up my logic analyser and take a look to see what the SCL and SDA lines are doing

But really, I've finished what I was going to do with this board, because I have fitted one of them in a box with a bluetooth receiver and it works fine in my car !

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.

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Re: Rogers postbag - FM radio band transmitter

Post by raphik » Sun Feb 19, 2017 12:54 am

@ RogerClark
Congrats for finishing your BT2FM project!

I finally succeeded to connect my MCU (an OpenWRT router) with the FM board. It is important to let both devices start before connecting their i2c buses in order to avoid collisions.
i2cdetect detects QN8027 on address 0x2c, just where it was supposed to be.
Image

As this is not really an STM32 project I may stop my postings here. A least until I buy my first STM32duino!

@everybody Care yourselves !

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RogerClark
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Re: Rogers postbag - FM radio band transmitter

Post by RogerClark » Sun Feb 19, 2017 2:00 am

@Raphik

How did you get your OpenWRT box to connect via I2C, do you have a some sort of USB to I2C dongle ?

I know there is a STM32 dongle which has USB to SPI, or I2C , so perhaps you are using that.
Or were you able to access the GPIO somehow e.g. are you running a RPi was OpenWRT?

Come to think of it a RPi or OrangePi etc is probably ideal hardware for this, as you don't need the expense of a full Wifi router for that project.

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