​ ​ ​ ​ Help please programming surface mounted picaxe chips
Page 1 of 3 1 2 3 LastLast
Results 1 to 10 of 25

Thread: Help please programming surface mounted picaxe chips

  1. #1
    Senior Member
    Join Date
    Jun 2012
    Location
    United Kingdom
    Posts
    244

    Default Help please programming surface mounted picaxe chips

    Hi

    Thanks for looking. I am wondering how to go about programming surface mounted chps. I am making a PCB and Id like it to be as small as possible. I may make many of these PCBs and will be using the surface mounted 14M2 and surface mounted 18M2. Im not sure how to go about programming these very small chips as I don't want to have any components on the board which may affect the end size. eg resistors, pins, etc used to program the chips.

    Is there a way to pre-program the chips before mounting them onto the PCBs. ie is there a commercial chip programmer for this size of chip available. Or can someone explain a method of programming these small chips. I have only ever used the large r size chips in the past and so I am new to the surface mouthed world.

    Thank you.

  2. #2
    Senior Member
    Join Date
    Apr 2012
    Location
    Cēsis, Latvia
    Posts
    814

    Default

    Dear @JPU,

    What I have done in the past, is I have had test pads routed for SerIn, SerOut and, of course, GND. Then you can design another PCB with all the extra components you want and 'pongo pins' to match the test pads. Some guide pins through mounting holes or something similar would probably be a good idea. Now you only have to position your board on top of the test/programming board, press on it lightly and press F5 on your computer.

    This would not take too much time, if producing low volume products and would actually be part of the deal anyway if some further semi-automated testing procedure of the functions of the board would be required.

    Alternatively, there has been talk on this very forum, RevEd would burn your chips for a fee before shipping them to you. In my mind this would only work for a very simple solution as normally you would want to be able to update your product the the latest firmware. In theory, there is also BAS800 sold by RevEd, that would support burning your chips with assembler code, but as I understand it is partly supported in PE5 and not supported at all in PE6.

    Good luck with your project,

    Edmunds

  3. #3
    Senior Member
    Join Date
    Aug 2011
    Location
    US
    Posts
    439

    Default

    I sell a low volume commercial product that uses a surface mount 20M2. The three resistors for the programming circuit are included on each board, and terminate at a very small connector also used to interface the board with the outside world (power, ground, sensors, switches, etc).

    I had originally considered pre-programming the 20M2 before they were soldered onto the board, and I am very glad I did NOT do this! Even the simplest code is subject to improvement as time goes by, and having to remove the chip from the board just to re-program it would be problematic at best. Sockets for surface mount chips do exist, but the size and expense is much greater than the three resistors.

    On a final note, the SerIn pin must never be allowed to float, so you will need the 10Kohm pulldown anyway, and once that is in place, the 22Kohm follows by default. A 180 ohm current limit on the Serout pin, while not stictly required, is good practice if there is any chance of the outside world trying to inject electrons into that pin on the final product

  4. #4
    Senior Member
    Join Date
    Feb 2012
    Location
    London
    Posts
    2,374

    Default

    Hi,

    +1 to the above posts. These days, no (sensible) large volume manufacturer would produce a PCB that couldn't be reprogrammed in some way. The PICaxe "programming" serial interface also can be very useful for testing and debugging.

    "Pads" are the answer, or even spring-loaded pins onto the existing pads/tracks. You really need only one SMD resistor to pull-down the Serial Programming pin. Make that resistor 100k (or 1M or probably 10M) and the PICaxe will still be happy, but you can then connect an external programming interface (including the 10k and 22k) via the three pads/pins.

    Cheers, Alan.

  5. #5
    Senior Member
    Join Date
    Jun 2012
    Location
    United Kingdom
    Posts
    244

    Default

    Hi All,

    Thanks for your ideas and advice. I understand most of the information given but I don't understand how the picaxe can be programmed if a 10k pull down is in place. If the 10k and Picaxe is in place on the end product PCB and then I overlay a second PCB with spring loaded pins which make contact with pads on the end product PCB, then wont the "serial in" pin still be pulled down by the 10k resistor and this will prevent programming?

  6. #6
    Senior Member
    Join Date
    Jul 2011
    Location
    Los Angeles, CA
    Posts
    1,812

    Default

    Quote Originally Posted by edmunds View Post
    Then you can design another PCB with all the extra components you want and 'pongo pins' to match the test pads.
    Good call, edmunds. I bet you meant pogo pins. This Disney Pongo pin is certainly adorable, but I'm not sure how much help it would be here http://renacollectibles.com/Disney-1...-P1802156.aspx

    Pongo Pin.jpg

  7. #7
    Senior Member
    Join Date
    Jul 2011
    Location
    Los Angeles, CA
    Posts
    1,812

    Default

    Quote Originally Posted by JPU View Post
    Hi All,

    Thanks for your ideas and advice. I understand most of the information given but I don't understand how the picaxe can be programmed if a 10k pull down is in place. If the 10k and Picaxe is in place on the end product PCB and then I overlay a second PCB with spring loaded pins which make contact with pads on the end product PCB, then wont the "serial in" pin still be pulled down by the 10k resistor and this will prevent programming?
    Actually that 10K resistor is part of the standard download circuit, along with the 22K resistor to the programming header. The 10K pulldown is still required even without the 22K for normal operation.

  8. #8
    Senior Member
    Join Date
    Feb 2011
    Location
    Cardiff,UK
    Posts
    4,174

    Default

    Quote Originally Posted by JPU View Post
    Hi All,

    Thanks for your ideas and advice. I understand most of the information given but I don't understand how the picaxe can be programmed if a 10k pull down is in place. If the 10k and Picaxe is in place on the end product PCB and then I overlay a second PCB with spring loaded pins which make contact with pads on the end product PCB, then wont the "serial in" pin still be pulled down by the 10k resistor and this will prevent programming?
    Take a look at the download circuit, page 8 of manual 1.

    The 10K resistor is meant to be left in place on the PCB, it does not affect programming.

    Its far better to build your circuit complete with the download circuit, the 10K and 22K resistors on the PCB, I would be very surprised if you cannot fit in the 2 resistors somehow.
    Picaxe in Space is now Silent (but probably still running)
    http://www.50dollarsat.info/

  9. #9
    Senior Member
    Join Date
    Apr 2012
    Location
    Cēsis, Latvia
    Posts
    814

    Default

    On a second thought - how much space do two 0402 or 0201 resistors with a common node take compared to 18pin SOP? Do you have manual assembly in mind? Still, 0402 is no problem and 0201 is doable with good repeatability if you have to. Just some equipment and little practice. It sounds like the wrong issue to spend time on. I understand you want to avoid the connector - that is bulky. Test pads are your industry standard answer that normally works. There is so much space under the SOP, that you can easily route the traces under it and to the bottom of the board. Components on both sides of the board are also an option.

    Edmunds
    Last edited by edmunds; 07-01-2017 at 20:43.

  10. #10
    Senior Member
    Join Date
    Apr 2012
    Location
    Cēsis, Latvia
    Posts
    814

    Default

    Quote Originally Posted by erco View Post
    Good call, edmunds. I bet you meant pogo pins. This Disney Pongo pin is certainly adorable, but I'm not sure how much help it would be here http://renacollectibles.com/Disney-1...-P1802156.aspx

    Pongo Pin.jpg
    +1
    Yes, I did. Something like these.

    Edmunds

Bookmarks

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •