Re: configuring an Efinix T20

From	john larkin <jl@650pot.com>
Newsgroups	sci.electronics.design, comp.arch.fpga, comp.sys.raspberry.pi
Subject	Re: configuring an Efinix T20
Date	2024-09-09 14:17 -0700
Message-ID	<s8pudj9gdm51ob02ng1f26i162jba1f8n2@4ax.com> (permalink)
References	(1 earlier) <vbhnef$190eu$1@dont-email.me> <h9todj9u2bs48i3itlgtorblj2buec7ios@4ax.com> <vbi62l$190eu$2@dont-email.me> <amhudj1mcq8uit59nbmm8d6j5erok8o0o1@4ax.com> <vbnk8m$2hhvl$1@dont-email.me>

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On Mon, 9 Sep 2024 20:02:30 -0000 (UTC), piglet
<erichpwagner@hotmail.com> wrote:

>john larkin <jl@650pot.com> wrote:
>> On Sat, 7 Sep 2024 19:29:41 +0100, John R Walliker
>> <jrwalliker@gmail.com> wrote:
>> 
>>> On 07/09/2024 16:58, john larkin wrote:
>>>> On Sat, 7 Sep 2024 15:19:59 +0100, John R Walliker
>>>> <jrwalliker@gmail.com> wrote:
>>>> 
>>>>> On 06/09/2024 23:50, john larkin wrote:
>>>>>> 
>>>>>> I'm planning to use a Raspberry Pi RP2040 processor chip to configure
>>>>>> and then talk to an Efinix T20-FG256 FPGA.
>>>>>> 
>>>>>> Has anyone done this, or at least configured a T20 from a
>>>>>> microprocessor?
>>>>>> 
>>>>>> The RP2040 only has 30 GPIO pins, and many are dedicated to other
>>>>>> stuff, so we want to share a lot of things on one giant SPI bus,
>>>>>> including the FPGA config and then an SPI port on the FPGA to read and
>>>>>> write registers.
>>>>>> 
>>>>>> It looks like four of the T20 config pins need pullups. I wonder why
>>>>>> their guidelines show four separate resistors. Why not one resistor?
>>>>>> Why have resistors at all?
>>>>>> 
>>>>>> SS_N needs a pulldown. Why not ground it?
>>>>>> 
>>>>>> https://www.dropbox.com/scl/fi/x0gvvwqg42vhryu6610ve/Efinix_Config_1.jpg?rlkey=udy24brtumvdzfd2sp4l6yhwf&raw=1
>>>>>> 
>>>>>> 
>>>>>> It's always a moment to celebrate when a "config done" LED lights up.
>>>>>> 
>>>>>> I could easily get this wrong, so it would be great if I posted some
>>>>>> schematics and notes and someone could eyeball them for me.
>>>>> 
>>>>> If you need some more i/o pins, why not use the RP2350B?  They
>>>>> definitely exist - I have one in front of me:
>>>>> https://shop.pimoroni.com/products/pga2350?variant=42092629229651
>>>>> 
>>>>> John
>>>> 
>>>> It only has two more package pins, as I recall. How many GPIOs?
>>> 
>>> No.  The RP2354B has 24 more package pins and 18 more GPIOs than
>>> the RP2040.
>>> 
>>> Its an 80-pin package with 48 GPIOs.
>> 
>> I was thinking about the RP2350, which has 60 pins. That's the chip on
>> the Pico 2.
>> 
>> I didn't even know that there was another small chip, the 2354B. That
>> might be the next step for our product line, in a year or two after
>> the new chips are debugged and available in quantity.
>> 
>> The 2350 data sheet is 1349 pages, possibly a world record.
>> 
>> I can't immediately find a data sheet for the 2354B.
>> 
>>> 
>>>> It's new and a bit buggy and not widely available, so we'll stick with
>>>> the 2040. The only upsides are the higher clock rate and the faster
>>>> floats, which aren't critical in the product line that we are
>>>> developing now.
>>> 
>>> Yes, there are some bugs.  The most critical is probably the one
>>> relating to on-chip pull-downs, but it can be solved with external
>>> resistors.  The ADC is improved.  There are more and better
>>> i/o state machines.  There is a lot more on-chip RAM and there
>>> will soon be the option of flash in the same package.
>>> There may not be production quantities of the RP2354B readily
>>> available yet, but there are certainly some around for prototypes.
>>> As I mentioned, I have one.
>> 
>> Does the 2350 have a switching regulator on-chip? Microns away from
>> the ADC?
>> 
>> 
>
>Yes, that’s the one where they found the inductor “polarity” mattered!

People add dithering noise and data lowpass filtering to improve ADC
linearity and resolution. Sounds like they included that for free.

(A clever pulse-height spectroscopy trick is to add known analog noise
to a signal, digitize, and digitally subtract it out later. Best of
both worlds.)

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Thread

configuring an Efinix T20 john larkin <jl@650pot.com> - 2024-09-06 15:50 -0700
  Re: configuring an Efinix T20 John R Walliker <jrwalliker@gmail.com> - 2024-09-07 15:19 +0100
    Re: configuring an Efinix T20 john larkin <jlarkin_highland_tech> - 2024-09-07 08:58 -0700
      Re: configuring an Efinix T20 John R Walliker <jrwalliker@gmail.com> - 2024-09-07 19:29 +0100
        Re: configuring an Efinix T20 john larkin <jl@650pot.com> - 2024-09-09 12:20 -0700
          Re: configuring an Efinix T20 piglet <erichpwagner@hotmail.com> - 2024-09-09 20:02 +0000
            Re: configuring an Efinix T20 john larkin <jl@650pot.com> - 2024-09-09 14:17 -0700
  Re: configuring an Efinix T20 Lasse Langwadt <llc@fonz.dk> - 2024-09-12 00:44 +0200

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