Go Back   Home > Forums > >
Home Forums Rules Articles diyAudio Store Blogs Gallery Wiki Register Donations FAQ Calendar Search Today's Posts Mark Forums Read

Equipment & Tools From test equipment to hand tools

PC USB scope project.
PC USB scope project.
Please consider donating to help us continue to serve you.

Ads on/off / Custom Title / More PMs / More album space / Advanced printing & mass image saving
Reply
 
Thread Tools Search this Thread
Old 14th July 2019, 11:19 PM   #51
nigelwright7557 is offline nigelwright7557  United Kingdom
diyAudio Member
 
nigelwright7557's Avatar
 
Join Date: Apr 2008
Location: Carlisle, England
Designing a partly SMD pcb for my latest version threw up a shortcoming in my pcbcad software. The PIC TQFP package and AD9200 A2D SSOP package are both "off grid".
So when I try to connect the tracks to the pins I have to do it free hand which is inaccurate. The pcb was looking terrible by the time I got loads of tracks in.
The tracks to the chip pins were often a little skewed.
So I got stuck into the software and came up with a couple of new functions.
The first function using Control - B key produces a new track segment which lines up backwards to the component pin it came from.
The second function Control - R key produces a right angle from current track position to the next pin to connect to. Both are controlled by current mouse pointer position so you get a choice of which way the tracks goes.
The tracks are now all spot on and look much more professional.
__________________
PCBCAD51 download or CDROM 2019 version out now https://www.murtonpikesystems.co.uk
  Reply With Quote
Old 15th July 2019, 02:27 AM   #52
anatech is offline anatech  Canada
diyAudio Moderator
 
anatech's Avatar
 
Join Date: Jun 2004
Location: Georgetown, On
PC USB scope project.
HI Nigel,
At least you figured out how to correct that issue!

-Chris
__________________
"Just because you can, doesn't mean you should" my Wife
  Reply With Quote
Old 15th July 2019, 03:08 AM   #53
nigelwright7557 is offline nigelwright7557  United Kingdom
diyAudio Member
 
nigelwright7557's Avatar
 
Join Date: Apr 2008
Location: Carlisle, England
Quote:
Originally Posted by anatech View Post
HI Nigel,
At least you figured out how to correct that issue!

-Chris
Its just the fine pitched SMD that cause a problem.
It tends to be metric so doesn't fit in with the factors of 100 thou of an inch grid.
__________________
PCBCAD51 download or CDROM 2019 version out now https://www.murtonpikesystems.co.uk
  Reply With Quote
Old 15th July 2019, 12:01 PM   #54
anatech is offline anatech  Canada
diyAudio Moderator
 
anatech's Avatar
 
Join Date: Jun 2004
Location: Georgetown, On
PC USB scope project.
Yes, I have noticed this as well.
__________________
"Just because you can, doesn't mean you should" my Wife
  Reply With Quote
Old 26th July 2019, 03:53 PM   #55
nigelwright7557 is offline nigelwright7557  United Kingdom
diyAudio Member
 
nigelwright7557's Avatar
 
Join Date: Apr 2008
Location: Carlisle, England
Got my new pcb through today.
PIC programmed ok but wouldn't run.
Noticed crystal was a bit too far away from the PIC so soldered it close and it started oscillating fine.
Then USB wouldn't run. Had a look at my previous circuit and noticed I missed the 100nf off USB3V3 pin. I soldered cap on and USB started working.
The output on the pc was terrible with big steps in the sine wave and loads of noise.
I eventually tracked it down to MPLAB Harmony pin setting screen. While I had set port b as GPIO_IN I had missed setting a couple of pins to tristate inputs.
The scope runs really well at about 10 mega samples per second.
The pcb needs quite a bit of rework but thats all part of development.
Important lessons learned so that is valuable.

The next pcb threw up a couple of shortcomings in my CAD software.
1/ Via sizes aren't remembered so you have to set them all individually. I now save the via sizes and use them if a new track segment is added.
2/ Going through pcb setting each individual via sizes was tedious so added a blockmode function to set via sizes in a block.
__________________
PCBCAD51 download or CDROM 2019 version out now https://www.murtonpikesystems.co.uk

Last edited by nigelwright7557; 26th July 2019 at 04:00 PM.
  Reply With Quote
Old 26th July 2019, 04:19 PM   #56
jan.didden is offline jan.didden  Europe
diyAudio Member
 
jan.didden's Avatar
 
Join Date: May 2002
Location: Westende Resort, BE coast
We'd call that Concurrent Engineering ;-)

Jan
__________________
Cable: a potential source of trouble interconnecting two other potential sources of trouble - Erik Margan
Linear Audio pubs and articles . The SilentSwitcher now at diyaudio store SilentSwitcher. Keeping in touch with SY.
  Reply With Quote
Old 26th July 2019, 04:58 PM   #57
maxtch is offline maxtch  China
diyAudio Member
 
Join Date: Apr 2018
Location: From Shanghai with Love
What kind of PCB software are you using? While I used to use EAGLE I have completely switched to KiCad v5 now.

As of the USB MCU, is there any reason behind the choice of PIC32? For such a project I personally would prefer something much faster like STM32F405 for its 168MHz operation and USB 2.0 High Speed interface. STM32 also uses ARM cores which has excellent open source support in GCC, CMSIS-DAP, OpenOCD and GDB.
  Reply With Quote
Old 26th July 2019, 06:17 PM   #58
nigelwright7557 is offline nigelwright7557  United Kingdom
diyAudio Member
 
nigelwright7557's Avatar
 
Join Date: Apr 2008
Location: Carlisle, England
Quote:
Originally Posted by maxtch View Post
What kind of PCB software are you using? While I used to use EAGLE I have completely switched to KiCad v5 now.

As of the USB MCU, is there any reason behind the choice of PIC32? For such a project I personally would prefer something much faster like STM32F405 for its 168MHz operation and USB 2.0 High Speed interface. STM32 also uses ARM cores which has excellent open source support in GCC, CMSIS-DAP, OpenOCD and GDB.
The PIC32mz runs at 200MHz internally. The fastest it can grab port data is about 10MHz. It also uses USB 2.0 but I just use HID as its fast enough.
__________________
PCBCAD51 download or CDROM 2019 version out now https://www.murtonpikesystems.co.uk
  Reply With Quote
Old 26th July 2019, 06:18 PM   #59
nigelwright7557 is offline nigelwright7557  United Kingdom
diyAudio Member
 
nigelwright7557's Avatar
 
Join Date: Apr 2008
Location: Carlisle, England
This is the prototype pcb.
A couple of caps glued on for extra decoupling.
Crystal moved about an inch to be next to PIC.
Bottom right hand side IC and components was a clock for A2D but I decided to clock it from the PIC so I could synch better.
Click the image to open in full size.
__________________
PCBCAD51 download or CDROM 2019 version out now https://www.murtonpikesystems.co.uk
  Reply With Quote
Old 26th July 2019, 07:43 PM   #60
maxtch is offline maxtch  China
diyAudio Member
 
Join Date: Apr 2018
Location: From Shanghai with Love
Quote:
Originally Posted by nigelwright7557 View Post
The PIC32mz runs at 200MHz internally. The fastest it can grab port data is about 10MHz. It also uses USB 2.0 but I just use HID as its fast enough.
While STM32 has a slower internal clock it can access digital I/O at 84MHz. The STM32F4 line also comes with hardware FPU for onboard signal preprocessing. Even the much slower STM32F0 series has 24MHz digital I/O. If you want fast, there is STM32F7 series with 216MHz Cortex-M7 cores, built-in USB 2.0 high speed transceivers (STM32F4 required external USB3300 transceivers for USB 2.0 480Mb/s operation) and 108MHz I/O

As of the PCB, I think with signals at that speed you will need the board be implemented using as much surface mount parts as possible.

Also you can run the PIC on the same clock as the external ADC. This can eliminate your clock woes. On the other hand you can also run the ADC on the clock derived from the PIC.

As of USB interface, USB audio class can be a better option than USB HID as it allows a much higher throughput.

Last edited by maxtch; 26th July 2019 at 07:46 PM.
  Reply With Quote

Reply


PC USB scope project.Hide this!Advertise here!
Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off

Forum Jump

Similar Threads
Thread Thread Starter Forum Replies Last Post
New project 1megasample/second PC USB scope project. nigelwright7557 Digital Line Level 0 14th July 2018 10:42 PM
DSO150 - a poor 'scope, but is it enough 'scope? bugbear Equipment & Tools 14 5th June 2018 03:13 PM
New project USB scope. nigelwright7557 Equipment & Tools 12 6th February 2017 05:59 PM
USB Scope - Real scope and not too expensive Algar_emi Equipment & Tools 11 16th March 2010 11:40 PM
Great deal on Digital scope. Is this enough scope? hifimaker Pass Labs 1 1st May 2007 09:59 PM


New To Site? Need Help?

All times are GMT. The time now is 08:13 PM.


Search Engine Optimisation provided by DragonByte SEO (Pro) - vBulletin Mods & Addons Copyright © 2019 DragonByte Technologies Ltd.
Resources saved on this page: MySQL 15.00%
vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2019 DragonByte Technologies Ltd.
Copyright ©1999-2019 diyAudio
Wiki