Micro Bitscope - B+ and PWM

[RussellPiBot]

Project:
Pibot using Pi A+ communicating with a custom (stripped down) Arduino Uno using I2C via MCP23017. Bot mobility will be controlled by Arduino PWM and quadrature Hall Effect feedback to Arduino via serial to parallel output latch 74HC595N.

Question:
Can the micro Bitscope and B+ be used to view the various signals being generated within the Bot system? I am particularly concerned that the B+ is not fast enough to capture changes in PWM for proper viewing.

Thank you for any advice you may provide.

[fruit-uk]

I'm sure it will be OK.
This is a screenshot of a 1-wire data stream from a Bitscope BS10 on RPi2 and I think that's higher frequency than you are going to see... I'm sure I read somewhere this wouldn't be possible using a Bitscope :\

[RussellPiBot]

Ok - I guess what you are saying is that the proof is in the pudding (screenshot) - the B+ can handle viewing a changing PWM signal no worries - correct?

Cheers

[fruit-uk]

I would think so, the spec for the BS05 indicates it can capture UART, SPI and I2C as can the BS10.
I've only tried it on the RPi2 but I'm sure an A+ would be OK unless heavily loaded.
I don't have any PWM stuff here or I'd try.

Have you looked at the video tutorial and Magpi articles?

[RussellPiBot]

I would think so, the spec for the BS05 indicates it can capture UART, SPI and I2C as can the BS10.

I believe the signals mentioned above are more or less burst signals and can be easily captured by BS micro and displayed by the Pi. On the other hand, PWM changes quickly based on encoder feedback and bot speed/direction changes required. The rapidly changing PWM signal does not pose a problem for the BS-micro; however, unlike a PC or Mac the PI may not have the capacity (computing power) to be able to react quickly enough to the changes. If so, this situation may result in a jerky display rather than a smooth presentation of the changing PWM wave.

I have done a fair amount of poking around on the web to see if anyone had actually used the Pi and BS-micro to view PWM and have not found a proper answer.

At this point I think I will just go ahead and order a BS-micro and if it does not work well with PWM I will use my MacBook Pro instead of the Pi B+ whenever I need to view PWM.

Thank you for taking the time to respond to my question.

Cheers

[fruit-uk]

If you have a sketch that I can stick on a Uno that will simulate the sort of thing you are looking for, or even something that rattles the Pi's GPIOs, I'm happy to try it here - on RPi2 and a B+ if you like.

[RussellPiBot]

If you have a sketch that I can stick on a Uno that will simulate the sort of thing you are looking for, or even something that rattles the Pi's GPIOs, I'm happy to try it here - on RPi2 and a B+ if you like.

Thank you for the kind offer; however, I am new to Pi and Arduino and just setting up my home hobby shop (retired engineer who loves to learn and tinker) and do not have any sketches to forward you.

My Pibot project is moving along at a slow and deliberate pace - concept-reasearch-build-test-improve. Only an old guy has the time and patience for this approach.

So far I have built a work bench, combo variable power supply/battery charger, a 5V bot power supply, laid out circuit plans, assembled parts and designed a two deck chassis for a two wheeled bot. The photo of the bot control center includes a Pi A+ under the Pi-hat. This bot will have plenty of capacity for sensors, servos, etc.

Will it all work? Yes, eventually. However, not without issues that must be resolved. That is why I am going to purchase the Bitscope micro as it will be key in resolving issues to come.

Cheers,

E-hacker shop.jpg (62.86 KiB) Viewed 1242 times

PiBot control center.jpg (61.41 KiB) Viewed 1242 times

[fruit-uk]

All sounds fun, best of luck with it.

I forgot that you can also connect the Bitscope DSO app to a live setup in Australia and have a play. No idea what it does as I've not tred it.