6502.org Forum Projects Code Documents Tools Forum
It is currently Sat Nov 23, 2024 3:52 am

View unanswered posts | View active topics


Board index » 6502.org Users Forum » Hardware

All times are UTC




Post new topic Reply to topic  Page 9 of 9
  [ 133 posts ]  Go to page Previous  1 ... 5, 6, 7, 8, 9
  Previous topic | Next topic 
Author Message
Arlet
PostPosted: Sun Oct 20, 2013 3:38 pm 
Offline
User avatar

Joined: Tue Nov 16, 2010 8:00 am
Posts: 2353
Location: Gouda, The Netherlands
lordbubsy wrote:
That’s not bad, for a more permanent supply I would use this schematic from a commercial product.


I would move C4 to the other side of the diode, so it's connected to the 7806. That is, if you insist on 7806+diode. I'd rather replace it by a 5V regulator without the diode. The diode isn't really doing anything useful.
Top
 Profile  
Reply with quote  
lordbubsy
PostPosted: Sun Oct 20, 2013 4:51 pm 
Offline

Joined: Wed Sep 11, 2013 8:43 pm
Posts: 207
Location: The Netherlands
Arlet wrote:
The FPGA will then become a super peripheral, capable of supporting video, sound, SPI, GPIO, USB, timers, UART, Flash, and whatever else I'd like. Using the BE pin, the FPGA can take over the bus, and pre-init SRAM, perform DMA, and generate video.
That sounds really great, I can’t wait to see it happen and perhaps learn something from it.

Quote:
if you insist on 7806+diode.
you’re right, it doesn’t make much sense in this case.
But further you have some flexibility on providing your circuit with power.

_________________
Marco
Top
 Profile  
Reply with quote  
GARTHWILSON
PostPosted: Sun Oct 20, 2013 6:59 pm 
Offline
User avatar

Joined: Fri Aug 30, 2002 1:09 am
Posts: 8544
Location: Southern California
Arlet wrote:
I would move C4 to the other side of the diode, so it's connected to the 7806. That is, if you insist on 7806+diode. I'd rather replace it by a 5V regulator without the diode. The diode isn't really doing anything useful.

Yes, put the bigger capacitor on the input of the regulator, not the output. Also, use a 5V regulator with no diode in the output (the diode makes for much poorer regulation), but:
Quote:
But further you have some flexibility on providing your circuit with power.

If you want to power it other ways to, put that diode across the regulator, with its anode at the output and its cathode at the input, then you can power the circuit from other sources if you like, without disconnecting the regulator and without hurting anything.

_________________
http://WilsonMinesCo.com/ lots of 6502 resources
The "second front page" is http://wilsonminesco.com/links.html .
What's an additional VIA among friends, anyhow?
Top
 Profile  
Reply with quote  
GARTHWILSON
PostPosted: Sun Oct 20, 2013 7:09 pm 
Offline
User avatar

Joined: Fri Aug 30, 2002 1:09 am
Posts: 8544
Location: Southern California
Arlet wrote:
I also recommend making a ground plane on top and bottom, and start by trying to route your signals on bottom layer. Many folks advocate using a power plane, but for 2 layer boards, I recommend sticking with 2 ground planes, and some fat power traces
and, I would add, put the bypass capacitors as close to the Vcc pins as you can.
Quote:
The reason is that your signals are going to chop up your ground plane, and if you only have one, you'll end up with a bunch of broken pieces. If you have two ground planes, and a bunch of vias connecting them, they'll work together as one solid plane.

(emphasis added). So where you have traces crossing on opposite layers, getting best AC behavior will involve putting four vias in the ground planes as close as practical to each of the four corners where the traces cross, so the ground return path for any given signal can stay as close as possible to the signal line. More on good construction and layout are in our sticky topic "Techniques for reliable high-speed digital circuits and the links there.

Again though, at 1 or 2MHz, you can get away with murder. [Edit: I must clarify that that refers to timings. If you have fast parts, you still have to keep your nose clean regarding build technique, as poor build technique can bite you even at very low clock rates.]

_________________
http://WilsonMinesCo.com/ lots of 6502 resources
The "second front page" is http://wilsonminesco.com/links.html .
What's an additional VIA among friends, anyhow?
Top
 Profile  
Reply with quote  
Arlet
PostPosted: Sun Oct 20, 2013 7:10 pm 
Offline
User avatar

Joined: Tue Nov 16, 2010 8:00 am
Posts: 2353
Location: Gouda, The Netherlands
GARTHWILSON wrote:
If you want to power it other ways to, put that diode across the regulator, with its cathode at the output and its anode at the input, then you can power the circuit from other sources if you like, without disconnecting the regulator and without hurting anything.

I don't think that's going to work if you offer, say, 12V at the input.

I think the idea of the diode after the regulator is that you can add another power source, also with its own diode, and attach it to the same point.

Another note about the schematic: I like to have the current flow from left to right (unless it's a feedback), so I'd flip the whole thing. Similarly, I always put my VCC at the top, and GND at the bottom, and also keep the VCC/GND symbols always facing the proper way. It just bugs me to see a GND symbol turned upside down, just because there was no room in the schematic.
Top
 Profile  
Reply with quote  
GARTHWILSON
PostPosted: Sun Oct 20, 2013 7:12 pm 
Offline
User avatar

Joined: Fri Aug 30, 2002 1:09 am
Posts: 8544
Location: Southern California
Arlet wrote:
GARTHWILSON wrote:
If you want to power it other ways to, put that diode across the regulator, with its cathode at the output and its anode at the input, then you can power the circuit from other sources if you like, without disconnecting the regulator and without hurting anything.

I don't think that's going to work if you offer, say, 12V at the input.

Woops, you're right-- I got it backwards. I'll edit it. I don't want to steer anyone wrong. I guess having the circuit drawn right-to-left turned my thinking backwards. I just need to slow down.

_________________
http://WilsonMinesCo.com/ lots of 6502 resources
The "second front page" is http://wilsonminesco.com/links.html .
What's an additional VIA among friends, anyhow?
Top
 Profile  
Reply with quote  
Arlet
PostPosted: Sun Oct 20, 2013 7:15 pm 
Offline
User avatar

Joined: Tue Nov 16, 2010 8:00 am
Posts: 2353
Location: Gouda, The Netherlands
GARTHWILSON wrote:
Again though, at 1 or 2MHz, you can get away with murder.

Agreed, but I always like to make the designs as robust as possible. Paying a little extra care to layout doesn't cost anything (except a bit of time).

Also, having a nice ground plane also improves immunity against external electromagnetic fields.
Top
 Profile  
Reply with quote  
Arlet
PostPosted: Sun Oct 20, 2013 7:16 pm 
Offline
User avatar

Joined: Tue Nov 16, 2010 8:00 am
Posts: 2353
Location: Gouda, The Netherlands
GARTHWILSON wrote:
I guess having the circuit drawn right-to-left turned my thinking backwards. I just need to slow down.

That's why I'd take the time to flip it over. Consistency helps prevent silly mistakes.
Top
 Profile  
Reply with quote  
GARTHWILSON
PostPosted: Sun Oct 20, 2013 7:55 pm 
Offline
User avatar

Joined: Fri Aug 30, 2002 1:09 am
Posts: 8544
Location: Southern California
Arlet wrote:
GARTHWILSON wrote:
Again though, at 1 or 2MHz, you can get away with murder.

Agreed, but I always like to make the designs as robust as possible. Paying a little extra care to layout doesn't cost anything (except a bit of time).

Agreed, and I would always do it the best I can too—I just don't want to scare newcomers off with too much theory if they're using 1MHz parts and it won't be necessary for just making it work.

Quote:
Also, having a nice ground plane also improves immunity against external electromagnetic fields.

and even more importantly, against radiating electrical noise that can get into sensitive nearby analog circuits, especially ones that might be controlled by this computer.

_________________
http://WilsonMinesCo.com/ lots of 6502 resources
The "second front page" is http://wilsonminesco.com/links.html .
What's an additional VIA among friends, anyhow?
Top
 Profile  
Reply with quote  
lordbubsy
PostPosted: Sun Oct 20, 2013 10:10 pm 
Offline

Joined: Wed Sep 11, 2013 8:43 pm
Posts: 207
Location: The Netherlands
This is a link to the crime scene.
http://shop.myavr.com/Kits/myAVR%20Boar ... p&artID=41

On the right you can check the circuit diagram.

It seems they have that circuit as a separate product.
http://shop.myavr.com/Kits/externPowerK ... tID=100003

Arlet wrote:
I think the idea of the diode after the regulator is that you can add another power source,
you’re right, the programmer on that board can also supply the voltage.

Arlet wrote:
I just don't want to scare newcomers off with too much theory if they're using 1MHz parts and it won't be necessary for just making it work.
Well, a lot of things that were explained I understand, but some I don’t. But I think it’s useful to get all that information. At a later time when I read it elsewhere I might get some recognition and perhaps understand it (better).

Till now I have switched course quite a few times while implementing new insights, which in itself is rather frustrating. But it saved me some unnecessary work already.

_________________
Marco
Top
 Profile  
Reply with quote  
lordbubsy
PostPosted: Wed Oct 23, 2013 6:33 pm 
Offline

Joined: Wed Sep 11, 2013 8:43 pm
Posts: 207
Location: The Netherlands
Reporting some progress:
I finished making a Xilinx parallel programmer and a XC9536 / 72 ISP Demo Board.
I also managed to reproduce Daryl’s 65SPI. I’m really happy. 8-P

Daryl is helping me programming some address decoding (thanks Daryl) and it’s going well. I’m studying an HDL-ABEL Primer and found Xilinx’s ABEL Reference Guide
http://www.xilinx.com/itp/xilinx10/help ... /whnjs.htm

I’ve attached the demo board to my prototype 6502 and transferred my very first bytes through 65SPI. As slave device I connected a gameduino. (not on the picture)
Attachment:
005.jpg
005.jpg [ 270.1 KiB | Viewed 792 times ]

Attachment:
2.png
2.png [ 12.9 KiB | Viewed 792 times ]

_________________
Marco
Top
 Profile  
Reply with quote  
barrym95838
PostPosted: Thu Oct 24, 2013 3:03 pm 
Offline
User avatar

Joined: Sun Jun 30, 2013 10:26 pm
Posts: 1949
Location: Sacramento, CA, USA
Please forgive me if the answer is obvious, but what is that sub-microsecond spike in the green channel?

Mike
Top
 Profile  
Reply with quote  
lordbubsy
PostPosted: Thu Oct 24, 2013 5:11 pm 
Offline

Joined: Wed Sep 11, 2013 8:43 pm
Posts: 207
Location: The Netherlands
I suspect that it is the start of the third byte, which has to be “1” on start. I’m not sure though.

OTH, I discovered that transmission wasn’t stable. Therefore I have replaced the power form the USB cable to a proper power supply. I lowered PHI2 to 1MHz instead of 1.8432MHz. Cleaned up the breadboard and added some more bypass caps. That didn’t help either.
After I connected ALL VCC’s, GND’s and open inputs to GND from 65SPI, transmission stays stable.

Attachment:
CRW_0009.jpg
CRW_0009.jpg [ 521.7 KiB | Viewed 766 times ]


Although I keep getting random spikes on all channels.

This is the start of the transmission which sends $80, $00, "abcdefgh etc."
Attachment:
Clipboard01.png
Clipboard01.png [ 16.93 KiB | Viewed 766 times ]

This is the whole transmission.
Attachment:
Clipboard02.png
Clipboard02.png [ 7.02 KiB | Viewed 766 times ]

All those blue spikes shouldn't be there.
I hope it will be more stable on the PCB. I’m at roughly 80% now.

_________________
Marco
Top
 Profile  
Reply with quote  
Display posts from previous:  Sort by  
Post new topic Reply to topic  Page 9 of 9
  [ 133 posts ]  Go to page Previous  1 ... 5, 6, 7, 8, 9

Board index » 6502.org Users Forum » Hardware

All times are UTC


Who is online

Users browsing this forum: Google [Bot] and 30 guests

You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum
You cannot post attachments in this forum

Search for:
Jump to:  
6502.org is an ongoing project by Mike Naberezny and contributors.