John Ford (@jmford94)

Principal Engineer at Steward Observatory, University of Arizona, working in motion control, signal processing, and engineering design. Industrial automation, scientific computing, and big science projects are my interests.

Re: Replacing specific bits in a number

Reply posted 6 months ago (05/28/2022)
You don't say what kind of machine you're using, but if it's a 32 bit machine, you can operate directly on the 32 bits using a set of masks to clear (with AND),...

Re: How to reduce PCI latency to read host memory (Linux)

Reply posted 7 months ago (05/02/2022)
There are a lot of things to consider.  Most are architecture specific, and you don't say what processors, chipsets, etc. you are using.Are you sure it's the transfers...

Re: Reference Designs for Solar Inverters?

Reply posted 7 months ago (04/29/2022)
Here's a TI reference design.  It might be overkill, but you might be able to scale it back.  Just came through my email this morning.Johnhttps://www.ti.com/tool/TIDA-010210Here's...

Re: Advice on Re-schooling?

Reply posted 9 months ago (03/08/2022)
I drove from Tucson to Phoenix and back twice over the weekend.  Lots of really empty space alongside the road, which gave me time to think more about this.I think...

Re: Advice on Re-schooling?

Reply posted 9 months ago (03/04/2022)
I don't know that re-schooling is necessary here.  Anyone with 20 years experience in C and PLM will be valuable to someone developing embedded systems.  I agree...

Re: How to build a network of tiny micros?

Reply posted 10 months ago (02/07/2022)
The ATTiny202 has a piece of memory that the debugger/programmer writes into that is not affected by a chiperase command.  That seems like a nice place to store...

Re: How to build a network of tiny micros?

Reply posted 10 months ago (02/07/2022)
Very cool idea.  I have never seen this before!  I'll have to look into the EFM8BB10.  I noticed the 8051 architecture is alive and well in this bargain-basement...

Re: How to build a network of tiny micros?

Reply posted 10 months ago (02/07/2022)
This is a good idea.  I'm fleshing out the protocol now, but it's affected by the physical implementation.  Agree that 150 slaves on the bus is a bad idea.Latency...

Re: How to build a network of tiny micros?

Reply posted 10 months ago (02/07/2022)
Yeah, I worry about the electrical performance of SPI with that many daisy-chained items.  But maybe it's better to daisy chain than multi-drop that many slaves....

How to build a network of tiny micros?

New thread started 10 months ago
Hi all.  I am designing a system for controlling a multitude (150!) of thermoelectric cooler units.  Each unit's current magnitude and direction must be individually...

Re: Formal Verification of Software

Reply posted 1 year ago (07/26/2021)
No, we were not able to use it, because we needed a 5 megabit per second uart and didn't have enough clock cycles to mux the inputs in.  We ended up with  enough...

Re: Formal Verification of Software

Reply posted 1 year ago (07/20/2021)
Hi Max.  I'm John Ford, Principal Engineer at Steward Observatory, University of Arizona.https://www.linkedin.com/in/john-ford-bb034121/

Re: Formal Verification of Software

Reply posted 1 year ago (07/20/2021)
No, I don't mind!  :)

Re: Formal Verification of Software

Reply posted 1 year ago (07/20/2021)
Hi Max.  I think most are aware of the concept, but I suspect that almost nobody actually does it.  There's an editorial in the July issue of the Communications...

Re: Interfacing MSP430 FRAUNCHPAD with MAX30102

Reply posted 1 year ago (07/08/2021)
A couple of things you can look at without instruments.  I agree with Al that an oscilloscope is one of those things that make the impossible simple...Check the...

Re: Why CRC with EPROM?

Reply posted 1 year ago (06/25/2021)
Hi Max.There are a few reasons that I see for it.  One, erasing and writing the eeprom takes a long time (in microcontroller time) and many operations, and if the...

Re: Cache memory vs volatile

Reply posted 2 years ago (03/19/2021)
I see 2 separate questions here.  Variables declared as volatile are not cached in registers between operations, so that if something writes to it outside the current...
There are a number of modbus slave libraries for Arduino on github.  I haven't used them, but I'd start there...

Re: Communication between ARM and DSP

Reply posted 2 years ago (12/15/2020)
The link you shared is for a benchmark copying data through the Linux kernel into userspace.  You will get many times more performance if you are working with the...

Re: Embedded C - Linking obj file

Reply posted 2 years ago (11/12/2020)
Many if not all linkers will link in all the objects that are in a single file.  You can split up the .obj into separate files and put them in a library to be more...

Re: Energy managment

Reply posted 2 years ago (08/25/2020)
The important thing is the energy balance, so that the system can be designed to take in enough to charge the battery or other storage you have.I agree with Matthew's...

Re: When is a State Machine not a State Machine?

Reply posted 2 years ago (07/20/2020)
I would say that it is.  The 2 states are LED_LO and LED_HIGH.  Not a very efficient use of CPU cycles, but it gets the job done.  
I think in general you should stick to signed or unsigned int, and let the compiler figure it out.  If you get to the end of the project and need a few more bytes...

Re: Improvement in Software design

Reply posted 3 years ago (05/05/2020)
I would get rid of the const in the argument, since you are overwriting stuff in the structure anyway.  This would make it more obvious what the intent of the...

Re: Digital PID controller implementation in C++

Reply posted 3 years ago (12/04/2019)
The problem with just zeroing it is that sometimes the integral term provides a lot of the command signal to a process, and if you zero it, it can take a long time...

Re: Digital PID controller implementation in C++

Reply posted 3 years ago (12/02/2019)
Yes, to avoid a transient, the integral needs to be initialized to the value that when used in the PID calculation will give the current output value, ignoring the...

Re: MSP430 Understanding

Reply posted 3 years ago (11/12/2019)
I think that you can program up to 4 hardware registers it recognizes in the IIC hardware.  See this app note.http://www.ti.com/lit/ug/slau425f/slau425f.pdf
1) Before jumping into coding, thinking, reading/writing, and understanding documents like requirements documents and design documents (however brief.  No need...

Re: LCD character update speed with AT89S52 micro

Reply posted 4 years ago (12/30/2018)
Another idea is to not use an interrupt, but poll the buffer in some place in your program, i.e. if you have an idle loop, use the dead time to update the LCD. You...

Re: Voltage swing for MSP430 PWM output

Reply posted 4 years ago (10/15/2018)
Maybe you need a pull-down resistor or load on the PWM output, otherwise it is floating?

Re: Learning FPGA

Reply posted 4 years ago (09/12/2018)
Hi StephaneAlthough I have been building embedded systems for 30 years, I have only recently started developing my own FPGA designs, so I think that I still have...

Re: Timer Implementation MSP430F5529LP

Reply posted 4 years ago (09/03/2018)
There are timers in the MSP430 that you can configure to create the time delay needed.  Then you can trigger the timer off the seat switch.  Then if the timer...

Re: Which FPGA kit to start with in 2018?

Reply posted 5 years ago (03/26/2018)
I agree with this suggestion for Lattice parts.  But be aware that they will not allow you to register for support if you have a gmail or university email.  I'm...

Re: Which Linux Editor should I use ?

Reply posted 5 years ago (01/12/2018)
You can google 'Eclipse VI plugin' for a list of eclipse plug-ins that support VI commands.

Re: Which Linux Editor should I use ?

Reply posted 5 years ago (01/12/2018)
Assuming you're not trolling us, here's a reply  :)I suggest you try different editors, and find one that suits you.  Consider other editors that you must use...
MartinThompson's post sums it up pretty well, but I have a perspective that I want to share.  I am working with really big (OK.  There are bigger, now!) parts...

Re: Power supply for router.

Reply posted 5 years ago (09/28/2017)
Do you need the 3.3 V linear regulator in there for some reason, or can you go straight to 3.3 from 12?  The 2576 is available in a 3.3 V and an adjustable version.Anyway,...

Re: Power supply for router.

Reply posted 5 years ago (09/26/2017)
I would look at the power supply with the scope while it is booting, with a trigger set on an excursion from 3.3 volts.  You may not have enough capacitance or...

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