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REPLACE A 18F67K22 with a 18F67k40 ?

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  • REPLACE A 18F67K22 with a 18F67k40 ?

    Hi charles ,

    i am looking to do an update on a pcb that uses a very full 18f67k22 and are considering migrating it to 18F67k40 , i am aware the k40 has 450bytes less ram , but rhas the same functions required

    The reason for the possible change is also cost reduction of the k40 series over the k22 series

    is this a good option to consider

    regards

    Sheldon

  • #2
    Sheldon, Personally I would stick with the 18F67K22 as it has self programming capability. I have used these as the host in my solar tracker projects. I would hate to loose the capability of using a boot loader as like you there is a lot of code. I use the Mecanique UMC boot loader software and there will be no more updates to it to support the K40 series processors. Unless you are making a million of your product I would stick with the 18F67K22. IMHO
    Dave Purola,
    N8NTA
    EN82fn

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    • #3
      The memory mapping of the 67K40 is worlds different than the K22. Depending on what you are trying to accomplish, it may require a massive software overhaul. We realized this when trying to modify DT_INTS-18 to work with the then-new K40s.
      We can crack this cotton PIC'n thang!

      Comment


      • #4
        As far as I can tell, the 67K40 is capable of self programming, though Dave's point about the Microcode Loader is valid.

        Mike's comment only applies to Assembly programming. PBP will handle the differences for you until you start writing assembly, as for an interrupt service routine.

        The cost difference is significant. I just checked and was surprised.

        I've used the 47K40 and it wasn't overly painful. I was concerned about the PPS configuration, but it actually saved me after I accidentally reversed the RX/TX pins on the PCB. I adapted an Assembly ISR from an 87K22 successfully. It was just a matter of SFR names and bank selections. There are differences in timer control and configuration that will need to be addressed if you use the timers. (The K40 timers are much improved.)

        If the cost savings is a factor and you're not using the Microcode Loader, I wouldn't hesitate too much before switching chips. It might entail a few days of frustration, but in my world that's normal. I call it a "weekend".

        As always, experimentation is advised. Don't order ten thousand assembled boards with the assumption the 67k40 will work. You can't be sure until you've tested.


        Charles Leo
        ME Labs, Inc.
        http://melabs.com

        Comment


        • #5
          thanks guys , yes the current 87k22 has 122k used , ,but a 67k22 was / is to be placed as the extra pins on the 87 are no longer required

          cost wise on 50- 100 purchase 67/87k22 are about $5.50aud each compared to $2.10aud - for 67k40

          code has assembly specific routines , dt_ints18, high / low priority running , plus a nmath ( long avoided to save space)

          the project does not have a boot loader as yet but its been on the to do list for a long time , issues of loading 4 x code to load up external flash chips and then a very large running code has sort of put me off to other parts than need to be done , so if a k40 is to be used a bootloader , mainly for update requirements is required at some point ,


          i am currently trying out a 27k40 for a small project and working to get that running , although most of the main routines will be clued together from other code, but need to use dt_ints version for the k40




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          • #6
            mikes version of dt_in18_k40 seem to address the timer interupt changes from what i see

            Comment


            • #7
              A few of us embarked on an extensive project to compile and codify Daryl Taylor's works, including the DT_INTS routines. It has been posted on the UK site in the form of an eBook. It can be found at:

              http://dt.picbasic.co.uk

              The specific "chapter" on modifying DT_INTS for a unique PIC is:

              http://dt.picbasic.co.uk/INT16/Customisation

              Hope this helps.
              We can crack this cotton PIC'n thang!

              Comment


              • #8
                Sheldon, I have just finished a few projects using the 18F27K40's and they are all working fine. I chose the 18F27K40 because of the increased flash memory. I am reluctant to put them into a project that will require code updates as there is no boot loader available except one that supposedly runs as an extension for MPLABX MCC. I have also seen some evidence of one available for the PROTON IDE. They both like a lot of work to get them to operate. For that reason I have a lot of extra pin's available on my solar tracker as it uses an 18F67K22 as well as my battery monitoring system controller.
                Dave Purola,
                N8NTA
                EN82fn

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