On 1/3/24 16:09, Chuck Peplinski wrote:
If the R-Pi guys are being responsive, I wonder if you find any answer
about the SPI interface for the Mesa boards? I found that linux-cnc
reported SPI errors when trying to talk to the 7C81. I'm new to the
Linux-CNC community, so maybe I'm doing something else wrong. But I got
the idea on the forums that there was some known issues with SPI on the
R-Pi5.
As a user using rpspi to a mea 7i90HD, I was amazed that when subbing an
rpi4b for a 3b required no changes to the spi bus. Part of the timing
that makes it work is the nanosecond lags between the clock and data
tines, extremely critical when the speeds are as high as they are, the
write from the pi to the mesa card is 42+ megabaud! And the
corresponding read is at half the 50 megacycle clocking speed of the
mesa card or 25 megabaud. the rise and fall times of the actual
transistors used are extremely critical and any change in the device
geometry that changes this waveform cannot be well seen with a 100 mhz
scope, one of the reasons I now own the fastest sampler Siglent makes, a
4 channel color channel with a 350 mhz bandwidth on all 4 channels,
worth $3400 USD when I bought it nearly 3 years ago. The differences
you can see are amazing. One of the things I noted was that to make it
work error free on the pi3 was that it worked well with the scope probe
attached to the clock but not so well w/o it, so I wound up with a 10 pf
cap to ground on the pi3, but didn't need it when the pi4b was
substituted. Based on that I concluded that the speed of the transistor
was part of the magic sauce that made it work.
Your remark makes me wonder if this same effect might be checked for
with a 10 pf cap on one or the other signals to effect a few picoseconds
delay difference between the clock and data lines and make it work.
There is I think a parity checksum as an error detector in the protocol,
with a parity error being corrected by a retransmit so if you see a
sudden burst of traffic its correcting such an error.. But PCW knows
that code 50,000% better than I so he is welcome to correct me. I'm just
guessing based on what I see on the scope screen based on 74 years of
using a scope to see what the electrical stuff is doing. 74 years ago
realtime was a 5" crt with a 5 megahertz bandwidth. A
Hickock 505. Sync-able but not triggered, that was a game changer.
It's been on my list to follow the build instructions and see if I could
find out more, but that hasn't happened yet.
Thanks,
Chuck
On 1/3/2024 1:39 PM, Rod Webster wrote:
Thank you for that pointer, I checked and found it installed but it
does not find any input or output devices.
Upstream have resolved the rpi-imager compatibility issue.
Their sound guy is away for a few days but has it on his to do list.
The willingness to sort this out has been amazing
I have to find time to merge the changes and rebuild it. I Am flat out
for
a while.
Rod Webster
*1300 896 832*
+61 435 765 611
Vehicle Modifications Network
www.vehiclemods.net.au
On Wed, 3 Jan 2024 at 22:27, Steffen Möller via Emc-developers <
emc-developers@lists.sourceforge.net> wrote:
On Tue, 2 Jan 2024 01:49:34 +0100
Steffen Möller via Emc-developers
<emc-developers@lists.sourceforge.net> wrote:
The regular raspbian OS comes with sound via HDMI. I am toying around
with packages to install to see if I am getting anywhere without much
configuration. KDE works after installing task-kde-desktop - no
sound, though.
Install the pavucontrol package. That hass the controls you need to
move the sound between ports.
Thank you for that pointer, I checked and found it installed but it
does not find any input or output devices.
Best,
Steffen
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Cheers, Gene Heskett.
--
"There are four boxes to be used in defense of liberty:
soap, ballot, jury, and ammo. Please use in that order."
-Ed Howdershelt (Author, 1940)
If we desire respect for the law, we must first make the law respectable.
- Louis D. Brandeis
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