Greaseweazle

[dwight]

I'm curious as to how the sampling code looks. Do you use the timers?
Dwight


________________________________
From: cctalk <cctalk-bounces at classiccmp.org> on behalf of Mattis Lind via cctalk <cctalk at classiccmp.org>
Sent: Wednesday, February 3, 2021 5:01 AM
To: Al Kossow <aek at bitsavers.org>; General Discussion: On-Topic and Off-Topic Posts <cctalk at classiccmp.org>
Subject: Re: Greaseweazle

Den ons 3 feb. 2021 kl 13:25 skrev Al Kossow via cctalk <
cctalk at classiccmp.org>:

> On 2/2/21 11:51 PM, Peter Corlett via cctalk wrote:
>
> > I have a pile of Blue Pill boards, and using it to read floppies was an
> > obvious application. However after running the numbers, it turned out
> there
> > isn't enough RAM to buffer an entire track from a HD floppy. It also has
> a
> > broken USB implementation just to liven things up a bit.
>
> a small performance list of STM32 parts and where they are used
>
> STM32F103C8T6  72MHz M3  64K Flash  20K RAM  FS     Original blue pill
> STM32F411CEV6 100MHz M4 512K Flash 128K RAM  FS     Latest WeAct black pill
> STM32F407VET6 168MHz M4 512K Flash 196K RAM  HS     Board Chuck likes
> STM32F730x8T6 216MHz M7  64K Flash 176K RAM  HS     Eric's GW / GW
> Lightning
>

The performance difference between the STM32F103 and any of the M4 (and M7)
chips is even bigger (than what the MHz tell) since there is a small cache
in the M4 (and M7) called ART which is intended to give close to zero wait
states when reading from flash. The STM32F103 has 2 wait states on flash
reads when running at 72 MHz. Unless you put code the code in RAM there
will be a performance hit on the 103. Unfortunately RAM is a scarce
resource on the 103 as well so you have to plan well to do that.

If one wants more buffer memory there is also the STM32F407ZET board which
uses the bigger 144 pin chip. On the back of those boards are pads for a
ISSI IS62WV51216 chip 512k x 16 chip.

What I think is kind of strange with the WeAct board is that they are not
identical in pinout to the blue pills. On one side all the pins are shifted
on step. I have no idea why they designed it that way.