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Make an expansion board with a serial port(s) for WL-500b/g - Page 3
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Thread: Make an expansion board with a serial port(s) for WL-500b/g

  1. #31
    yes, the xtal will be 12.75 mhz, no problem, but i think the uart is intended to work with a 18 mhz xtal. my question should be:
    - if i have an uart that's intented to work with an 18 mhz xtal, will it work in this case if i use it with a 13 mhz xtal?

  2. #32
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    Quote Originally Posted by Alice
    yes, the xtal will be 12.75 mhz, no problem, but i think the uart is intended to work with a 18 mhz xtal. my question should be:
    - if i have an uart that's intented to work with an 18 mhz xtal, will it work in this case if i use it with a 13 mhz xtal?
    Find and check the data sheet for your specific chip then...
    The top frequency limit is important. I am sure the UART chip will work fine at any lower frequency.

  3. #33
    i've searched for datasheet but I couldn't find it.
    oh well... i'll try and see what it gets.

    I presume that 1M means 1 uF capacitor, right?

  4. #34
    I would just need 2 pins of the serial port to control a 240V relais.

    Is this possible?

    Read more and post here.
    http://wl500g.info/showthread.php?p=11849#post11849

  5. #35
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    Quote Originally Posted by Oleg
    wl500gx should work in the same way as wrt54g, it does not need an external uart.
    Which uart pinout does the bootloader use? TX0/RX0 or TX1/RX1
    It's still a gx, but i can't measure voltage change, it's a constant 3.3v. If there was something data, its effective voltage should be less than that.
    Unfortunately, i don't have a scope...

    Does serial console enabled in your latest firmware?
    Josephus
    HuWiCo - Hungarian Wireless Community
    http://www.huwico.hu

  6. #36
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    Quote Originally Posted by Josephus
    Which uart pinout does the bootloader use? TX0/RX0 or TX1/RX1
    It's still a gx, but i can't measure voltage change, it's a constant 3.3v. If there was something data, its effective voltage should be less than that.
    Unfortunately, i don't have a scope...

    Does serial console enabled in your latest firmware?
    Should be TX0/RX0. Yes, console is enabled.

  7. #37
    For my understanding: is the UART now memory mapped? Or is it somewhere in PCI space?

  8. #38
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    Quote Originally Posted by dAF2000
    For my understanding: is the UART now memory mapped? Or is it somewhere in PCI space?
    Available in memory at base address 0xBF800000.

    How many people have actually installed an UART on their wl-500g? Are they working flawlessly? I'm thinking about adding one, but it would be nice to hear a few experiences first. (Yes I know it is easier to add a serial port with a pl2303, I have already done this but want to try something new...)
    Technik: How did you know that a 12.75 MHz is the right rate? (Where in the source did you find it?)
    I would like to use a PC16552D (dual UART); can the two UARTs share the interrupt? (INTR1 and INTR2 outputs OR'ed together and then connected to PIN17)

  9. #39
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    Some guy in the Dutch forum already has a serial port hooked up: http://wl500g.info/showthread.php?t=3587

    Perhaps you can contact him...

  10. #40
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    Quote Originally Posted by wtzm
    ...
    Technik: How did you know that a 12.75 MHz is the right rate? (Where in the source did you find it?)
    I would like to use a PC16552D (dual UART); can the two UARTs share the interrupt? (INTR1 and INTR2 outputs OR'ed together and then connected to PIN17)
    Sorry for the late response...
    The original source was in some discussion about WRT54G. I expected that the same frequency could work in WL-500 as well --> true. If you use different XTAL, you will probably have to patch the serial driver - AFAIK there are Baud Rate Divisor constants.
    Interrupt sharing should be OK. Please read this thread as well:
    http://wl500g.info/showthread.php?t=1993

  11. #41
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    Quote Originally Posted by Technik
    Sorry for the late response...
    Appreciated nevertheless.
    I suppose the kernel finds and initializes the serial ports in sbmips.c, funktion sb_serial_init, is this right? The wl500g has a "extif core" (don't know what this is all about, but as the signals are named EIF_OE, EIF_WE, et cetera, I assume this is EXTIF related), so add(regs, irq, 13500000, 0) is called. The third variable is called baud_base. Hm... 13,5MHz? Was the 12,75MHz XTAL just close enough to this value to make it work, or are the 12,75MHz defined somewhere else?
    By the way - I would find further information about the inner workings of the bcm47xx series really usefully, especially I don't really understand what these "cores" are and what "core switching" is about. I allready did a fair bit of reading the kernel sources but if there is some kind of tutorial available for this platform (without signing any kind of NDA...), this would really help me.

  12. #42
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    Quote Originally Posted by wtzm
    By the way - I would find further information about the inner workings of the bcm47xx series really usefully, especially I don't really understand what these "cores" are and what "core switching" is about. I allready did a fair bit of reading the kernel sources but if there is some kind of tutorial available for this platform (without signing any kind of NDA...), this would really help me.
    This is a concept of silicon backplane bus, which should be covered for the SiByte sb1250 cpu. Try this link http://www.broadcom.com/products/Ent...ons-Processors

  13. #43
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    Thanks for the link Oleg; I have taken a look at the BCM1125H/BCM1250 User Manual; It is quit a nice read and although I'm not sure how much of this applies to my wl500g, Chapter 11 - "Generic/Boot bus" was very interesting and helped me in understanding the bus which the external uart(s) and parport is connected to.

  14. #44
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    Well, it has nothing is common with wl500g, except silicon bus backplane (chip internal bus) concept.

  15. #45
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    Ah, ok, this pretty much confirms my "guesstimation".

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