Hot!Bm78 basics!

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geoffers
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2017/04/16 02:55:06 (permalink)
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Bm78 basics!

Hi all,
I've recently got a couple bm78 modules to try and integrate into a pic based device.

My previous proto used a rn42 set up as Bluetooth master, I got it working fairly easily, it communicates with a Bluetooth printer and a Android app.

I've bodged the bm78 on a bit of prototype board and given it power, my phone can find it but the app won't connect with it. The status output shows it in access state.

I don't know much about Bluetooth, the rn42 is I think Bluetooth 2.1? The bm78 is 4.

I've been through the datasheets I can find for the bm78 and can't find any info about putting it in master mode? Is that a 'old thing' that's gone with Bluetooth 4?

If so what settings do I need to use, if not is the bm78 suitable? Its not as user friendly as the rn42 but is smaller and a lot cheaper :-).

I don't mind writing code to talk to it and configure it as long as I'm not going to find it won't act as master to talk to the little printer. (I already have code to talk to the rn42)

Cheers Geoff
#1

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    RISC
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    Re: Bm78 basics! 2017/04/16 04:26:43 (permalink)
    3 (1)
    Hi,
    Actually there are 2 versions of "BM78".
    BM78 is a kind of low level register access version
    RN4678 is the same physical module but with different firmware, similar style as RN42, i.e. ASCII commands.
    If you like the RN42 style, I suggest you use RN4678. Make sure to update it to latest firmware version
    Regards
     
    #2
    geoffers
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    Re: Bm78 basics! 2017/04/16 12:28:29 (permalink)
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    Hi,
    Thanks for the reply,
    I'm not in love with the ASCII commands and for a change have quite a few i./o's available so as long as it will work I would persevere with the bm78.

    I've been studying the data sheets again and although can find no mention of how to set it as master, there is a ' just work" setting!

    Could this be what I'm after? I program in asm so I'm used to working at a low level :-), I just don't want to put in the time if its not going to work.

    Does anyone know where I can find out how to use the i2c ? The documentation is not very good on this, most un microchip.
    Thanks Geoff
    #3
    RISC
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    Re: Bm78 basics! 2017/04/16 15:00:51 (permalink)
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    Hi,
    You must control BM78 using UART (this is clearly explained in documentation).
    For I2C, it is reserved for Apple special chip to authentication (see BM78 pictail evaluation board page 30).
    I found 4 documents to help using BM78 :
    * BM78_datasheet_60001380A.pdf
    * IS1678S_UARTCommandSet_UserGuide.pdf
    * IS1678S_ApplicationNote.pdf
    * BM78_Pictail_EVB_manual_70005246A.PDF
    If you want to use BM78 you should either buy a BM78 pictail to have a reference platform on which there are examples and SW applications controlling the pictail from a smartphone.
    Regards
    #4
    geoffers
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    Re: Bm78 basics! 2017/04/17 12:23:04 (permalink)
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    Thanks,
    I hadn't got the evb manual so hopefully that will shed a bit of light on things.

    I had a look at the pictail on rs, it seems a bit steep on price here in the UK at £74, I expect your right and I will end up buying one.
    At that money I can do a few hours fiddling before I do.

    Cheers Geoff
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    RISC
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    Re: Bm78 basics! 2017/04/17 13:16:49 (permalink)
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    Hi,
    Check your schematic agains the BM78 evaluation board schematic in the evalboard user manual.
    It might help confirm your hardware.
    Make sure to connect a USB <=> RS232 bridge to control your board
    Regards
     
     
    #6
    geoffers
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    Re: Bm78 basics! 2017/04/17 13:59:30 (permalink)
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    Thanks,
    That's the line I was thinking along , I have one of those usb cables with a fdtl (I think!) Chip in it that adapts its tx/rx levels to suit. Handy for this sort of thing, will let you know how I get on.
    Cheers Geoff
    #7
    geoffers
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    Re: Bm78 basics! 2017/05/28 05:33:26 (permalink)
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    Hi again!

    I've been fiddling with this a bit and run into problems...
    I suspect I may have 'bricked' (not a great description, a brick is useful!) the first bm78. I'm not sure how? I had it connecting to the phone , in link state according to the two indicator pins, I'm using BT chat on the phone but tx on the module just stays high with some 5khz noise, sending data to the module via fdtl lead and putty doesn't work, is nothing appeared on BT chat.

    I have seen another post about noise on a bm78 tx pin.

    I'm going to try another one soon, I will post if I can get anything working, these seem to be fiddly things. I think the new born is sapping brain power and time too.....
    Cheers Geoff
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    geoffers
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    Re: Bm78 basics! 2017/05/30 06:00:09 (permalink)
    3 (1)
    OK update,
    I've got the little monkey to connect to my phone, I can send/receive data via putty and my fdtl lead.

    Various apps for serial Bluetooth work, the one I want to work with however refuses to connect to dual SSP .

    Its quite old but connects first time to a rn 42 configured as master. I was hoping the bm78 would do the same as it supports classic Bluetooth which I believe is SSP?

    I guess I need to do some configuration to the bm 78, does anyone have a idea what?
    Will 'just work' setting do that?

    The rn 42 had quite specific settings as master/slave but I see none of that in the bm78 data sheets?

    I tried to use the ui tool but that is expecting to see a mcp2200 serial bridge, not my fdtl.

    Is the only way to configure through that tool? I would prefer to do it via the pic UART.

    Cheers Geoff
    #9
    RISC
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    Re: Bm78 basics! 2017/05/30 07:15:22 (permalink)
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    Hi,
    BM78 is essentially register oriented and therefore it is necessary to develop using PC UI tool.
    RN4678 is a command parser and is easier to develop using a PIC as it includes a command parser on top of the BM78 registers
    regards
    #10
    geoffers
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    Re: Bm78 basics! 2017/05/31 09:41:11 (permalink)
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    Thanks,
    I had a look at the rn4678 data sheet and it seems similar to the bm78 except for the command set as you would expect, maybe I've missed it but still nothing about it being a master in classic mode?
    Both the things I need to connect to are slaves so need the module as a master.
    As a aside funny things happen after power up of the module, my pic sends a 15 character packet out the UART at 115200 baud. The first packet causes a lot of Radom characters to appear on the phone, followed by the packet, subsequent packets don't , if I disconnect from the phone and reconnect, no Radom stuff, if I send the same data from putty no Radom stuff, if I receive pic>putty just my characters.
    They only appear after power up?
    Cheers Geoff
    #11
    geoffers
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    Re: Bm78 basics! 2017/06/02 07:20:07 (permalink)
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    Another update....
    I've been through data sheets again for some clue as how to move forward, not much progress?
    All I want to do is use this thing as a master in classic Bluetooth mode , I feel I'm banging my head on the wall!
    I've tried pulling enquiry control input low but it doesn't help?

    How do I get in touch with someone who knows what to do?

    I'm going to fiddle around with the configuration later, if I can change its name I will be happy :-) I think I've figured how to do that!
    Cheers Geoff
    #12
    geoffers
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    Re: Bm78 basics! 2017/06/09 08:33:34 (permalink)
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    And again...

    I've been able to use the UART on my pic to write/read the bm78 eeprom.

    I can change the name etc. I used the ui tool then saved settings and compared them to the default file (you can read them with notepad). You can then write the appropriate values to eeprom.

    I bought a mcp2200 UART to USB bridge but the ui tool just give a error message and stops working? Anyone else had problems like that? The bridge works fine with real term.

    The is1678 commands can't be used until you have either used the ui tool or in my case written to eeprom the timeout value, default is 0s. This isn't mentioned in the data sheet.....

    I have still to get it to work with my printer, any hints as to what settings I need to use will be welcome.
    Cheers Geoff
    #13
    geoffers
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    Re: Bm78 basics! 2017/06/09 08:33:36 (permalink)
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    And again...

    I've been able to use the UART on my pic to write/read the bm78 eeprom.

    I can change the name etc. I used the ui tool then saved settings and compared them to the default file (you can read them with notepad). You can then write the appropriate values to eeprom.

    I bought a mcp2200 UART to USB bridge but the ui tool just give a error message and stops working? Anyone else had problems like that? The bridge works fine with real term.

    The is1678 commands can't be used until you have either used the ui tool or in my case written to eeprom the timeout value, default is 0s. This isn't mentioned in the data sheet.....

    I have still to get it to work with my printer, any hints as to what settings I need to use will be welcome.
    Cheers Geoff
    #14
    myZigbee
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    Re: Bm78 basics! 2017/06/12 09:04:46 (permalink)
    3 (1)
    BM78 and RN4678 are the same hardware. There are some differences though. I believe BM78 does not support master mode, but RN4678 does. To check if a module is able to be master, check if they could perform operations such as scan or connect.
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    geoffers
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    Re: Bm78 basics! 2017/06/13 09:32:27 (permalink)
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    Thanks, that's a shame, I'm just getting my head round programming the eeprom etc. I'm a bit nervous about using the rn4678 , are there supply issues?, here in the uk rs don't have any til September, farnell have some the a few more in August, none til next April then! I don't want to design the whole thing and find I can't get them!
    Cheers Geoff
    #16
    RISC
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    Re: Bm78 basics! 2017/06/13 11:46:39 (permalink)
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    Hi,
    There is a lot of stock of RN4678 on MicrochipDirect and also on Mouser
    Regards
    #17
    geoffers
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    Re: Bm78 basics! 2017/06/21 13:47:26 (permalink)
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    Thanks,
    Have got one from farnell now , hopefully I will get to it in the next week.
    Cheers Geoff
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    geoffers
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    Re: Bm78 basics! 2017/07/15 13:55:53 (permalink)
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    Next week, maybe next month!
    I got a rn4678, couldn't get anything out the tx of the module, thought I must have burned it as I accidentally put 5v on the vdd io, got a new one that's the same.

    In the rn4678 command ref it says flow control is disabled, however if I pull CTS low it all works, ie serial data comes out tx as expected.

    Bit of a moan, have I either got a couple duff modules or is the data sheet wrong? The data sheets for the bm78 aren't any better.

    If I missed the bit that says flow control is enabled as default I'd like to know where it is.
    Hopefully this might help someone else, I will mess about some more and maybe get it working with my printer :-)

    Cheers Geoff
    #19
    RISC
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    Re: Bm78 basics! 2017/07/15 14:28:57 (permalink)
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    Hi,
    I personally always get myslef an existing demoboard (when it exists) to get started and as a reference to my own design...
    I have used RN-4678-PICTAIL to get started and it worked out of the box.
    Having a working reference is a time saver when one designs his own board ;=)
    Can you please show your complete schematic / picture of your board ?
    I think there might something in your circuitry...
    Regards
     
    #20
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