maybe i am, in my job practice, 30% is about electronics, instrumentation & controls. with this, i need to prepare my self in line with the subject frequently with the help through DIGI-KEY CONTINUING EDUCATION CENTER.
with that, i am thankful for having it though online...
thanks to DESIGN NEWS & STAFF...LECTURERS AND COLLEAGUES...
thank you sir jon, sir alex and colleagues taking-up this course...happy good day!
once again, here i am for final day of the class...
you know, this is the benefits if the lessons are already in the archived, so you can finish them all as you like, hehehe...the truth is, i am staying the whole day in my flat focussing with this lesson and finish them all...very interesting and well informative on every discussion like i am in the university class room again...
anyway, i will take a little bit rest while downloading such material as reference to go though it...thanks again...
I guess if you are paying attention, the context lets you know. But, I have found myself having to search a few times only to find that we were a few slides ahead or behind of the one that I thought we were talking about.
You can get started with PIC by just downloading the free MPLAB IDE and Simulator and then the basic trial Compiler for free.
You can always get just bare parts DigiKey or anyone and as long as you are below 40MHz, perf bd or breadboard should be fine. Look at app notes and you can just use serial with a bootloader to program the chip.
I started with a PIC Programmer/Debugger and a startup dev board from Microchip and I feel like I invested wisely and saved myself a ton of headaches by just taking the plunge.
Looks like I have exhausted the pool of questions that remained unanswered. To all still monitoring this chat, thanks for your comments, questions, and answers that helped others. Have a pleasant weekend. Signing off. --Jon Titus, Herriman, UT.
A: Someone suggested using a heatsink. Buy an LM7805 is a TO-3 package and buy a compatoble bolt-on heat sink. The TO-3 package will dissipate more heat than a TO-220 tab package. Digi-Key sells part number 497-1005-ND for about $US 3.40.
A: Assume all pins are susceptible to damage by a direct or nearby static discharge or even by the buildup of static charges. Work on a static-dissipating mat and wear a grounded wrist strap. I know many people don't do this, but they might end up spending hours trying to troubleshoot a hidden problem causes by a zapped MCU. The 3M company makes static-dissipating mats for work surfaces.
Q: Jon, can that jumper shorting trick activate ifdef debug code?
A: The #ifdef is a conditional-compiler code and not part of the actual MCU program. You would test the input pin for the presence of the jumper with a simple c-language if statement and then branch to the diagnostic or self-test code.
Q: What would be your recommendation for measuring Battery voltage thru a micro A/D, say a 9-volt battery? Simply using a voltage divider causes current draw while the micro is shut down.
A: Yes, if you use two resistors to create a voltage divider you continue to draw current all the time. Use a small NPN transistor between the resistors and ground and turn it on with an output pin at logic 0. Then current will flow through the resistors and you can measure the voltage. Just account for the voltage drop across the NPN transistor when you calculate the resistor values needed to get a voltage you can measure.
A: More often than you might think. Recently the FBI made arrests at a company that imported counterfeit components from Asian suppliers. Some of those chips went into aerospace and military equipment!
Q: This question is a bit off subject, but what is the job market like for an independent application designer? Is there a niche for the small business person?
A: The problem is making contacts that lead to business. It's a difficult road to travel unless you have a solid reputation and a lot of experience. You're probably better off starting work with a company where you can learn on the job and then take those skills to your own business. It's good to have that experience on your resume. Whatever path you take, stay up to date on new technologies pertinent to your field. These days It's easy to fall behind.
Q: The problem with pcb manufacturers is it only becomes cost effective if you do multiple boards of the same type. Small batches etching at home is more cost effective.
A: By the time you get all the materials, create a good 1:1 negative or positive film, etch the boards, and drill them, let alone deal with through holes, a commercial board service proves more economical and without the problems of safe and legal chemical disposal. I have etched boards with a commercial UV-sensitive film and the results were OK, but not great. Maybe the process has gotten simpler and the photo-sensitive films better, but even for small hobby projects it's a pain.
Q: How to choose the I/O pins for self diagnose routines, such as JTAG interface? What's the software tools for micro-controller to browse through stack info? again what pins are involved?
A: The MCU manufacturers designate pins for the JTAG connections, but often they share functions with other devices, such as general-purpose I/O, analog-to-digital converter input, and so on. So, you might not have the pins available for JTAG in a real design. While using a development board or prototype, you want those pins free for the JTAG connections. For self diagnostics you use the MCU to check its connections, write a test message on any attached display, let someone test a keypad, and so on. There's more to it, of course, but the idea is to ensure the MCU and the attached devices operate properly before you go into the actual application code.
Q: @Jon: Is there any tips'n tricks available for other microcontrollers, like MSP430 family from Texas Instruments or for LPC family from NXP ?
A: Sure, and a lot of helpful application notes, too. Go to the MCU manufacturers' web sites and look through their literature, or search their sites for "tips tricks" (without the quotes). You'll find more than you imagined.
Q: with regard to the sw interrupt 2nd type, some AVR chips hardware automatically disable all interruptswhen an interrupt is entered, so the delay executing the entire routine in the interrupt may cause a timing problem. What other method do u like to use in a case like this??
A: Some MCUs do that--disable all interrupts when they enter an ISR. I'd bet you can turn the interrupt back on , though, via a bit in a register.
Q: Jon, Breadbords generate lots of nosie, any other way recommand?
A: Yes, they do, and for analog circuits, the capacitance between contacts can cause problems. To reduce noise and capacitance use the "dead bug" prototype approach. Ren a Google image search for "dead bug prototype" (without the quotes). One of my colleagues used 10-megohm resistors soldered to a copper PCB ground plane and binding posts (the ungrounded end) and built a circuit from resistor to resistor. Analog expect Bob Pease at National Semiconductor (now TI) used this technique a lot.
KevinJam, be careful - we have driver issues from our Freescale HCS12 boards - cadets here at the Academy get their laptops reimaged to Win7 64-bit and Freescale is not planning any upgrades to the USB drivers for their board. The latest and greatest may be different.
Q: @jon: do you prototype with through-hole parts? When do you go for SMD parts?
A: Both. I use through-hole devices as much as possible for prototypes because these old eyes have a tough time seeing the tiny SMT parts. I have glasses (see photo at tope) and use a magnifier, too. It's also easier to replace through-hole components if I need to modify something. I like the SMT chip adapters from SchmartBoard and use them to turn SMT chips into through-hole components. Their boards "self align" chip pins with contacts. Get some good solder flux, too. I recommend ChipQuik.
If you add extra rectifiers, you automatically drop the supply voltage by the voltage across two diodes (1.4 volts for a bridge) and those diodes give off heat! You could include one diode to prevent blowing the MCU circuit with a power supply of the wrong polarity. Better: Buy and use good-quality power supplies.
Q: It should be noted that it can be sometimes tricky to program older PIC chips such as PIC16F84 using pickit2/3 which most circuits on the web and in books are based on. Must use the application provided by the programmer rather than through MPLAB.
A: Good point. Check for compatibility between MCU programming tools and the MCU you want to use. Some older hardware will not program newer chips. Manufacturers provide this compatibility information.
Q: manya: Alright. Thank you. Jon just seemed to be emphasizing that Chinese microcontrollers aren't very good.
A: I want to emphasize the lack of support and lack of true compatibility with such products. If they fail, how do you get in touch with them? Do they support software upgrades and bug fixes? Probably not.
Q: I tend to use simple tools to start deciding my troubleshooting approach. It seems to be more intuitive to me by feeling my way around the situation. then go to appropriate test equipment for the detail.
A: Good point. No need to use an expensive sophisticated tool if something simple (and easy to set up) does the job.
Q: @Jon knowing the assembly language of an MCU is just for curiosity or is it useful?
A: I learned FORTRAN II on an IBM mainframe and then assembly language on a minicomputer. The assembly-language experience helped me better analyse what I wanted to do and it put me in complete control of the processor. I liked it and found the education helpful. Now, though, I'd rather use a high-level language such as C or even BASIC. I guessw it depends on how much you want to know about how the MCUs work down at the chip.
Q: Jon, for +5V Vcc, what is best range of pull-up resistor?
A: It depends. You need enough resistance to pull up an input to a logic-1 state. A 1-kohm resistor usually does fine, although CMOS circuits can use a 10 Kohm resistor. In the "old days," we used 1K resistors for all pullups. I still have a drawer full of them.
Q: If you have to chose an opamp chip,..how do you choose between ttl and cmos?
A: You wouldn't consider an op-amp as either TTL or CMOS. Instead, look at the characteristics you need, such as bandwidth, noise, etc. I bet Analog Devices, Linear Technology, Microchip, and Texas Instruments have op-amp selection guides and application notes. See also, "Op Amp Application Handbook," from Newnes-Elsevier (publisher). ISBN: 978-0-7506-7844-5.
Q: When you have completed testing and wish to commit to final circuit board design, is it better to outsource board design or long-run better to obtain own board design equipment?
A: Do it yourself. You know details about the circuit that a design house doesn't know. For example, where does the current flow. A design house might use a 10 mil trace where you are running an amp of current.
Don't bother building boards at home. There are companies that do it better and cheaper.
@kevinjam, I prototype first PCB at home, then use a fab house to make the PCB's, much better quality and I can't do anything more than double sided at home. All design files Gerber files are done at home. The chemical process is messy.
A: I didn't say germanium is good for regulator. Germanium diod is better for use in the comprator circuit for detection of low Battery. Because germanium is liner, even is very good for temperature sensor up to 100 degree celsius.
Q: A question about communications between micro's. If I need to have a group of modules each with a microcontroller communicating with a master microcontroller( and potentialy up to 15 feet between them), is RS485 a good protocol to use or would one of the others mentioned be better?
A: RS485 is fine for that type of application. You can find many good '485 driver ICs. Use high-quality wire for communications.
Q: When you have completed testing and wish to commit to final circuit board design, is it better to outsource board design or long-run better to obtain own board design equipment?
A: Having an outside service design the board will cost a lot of money. You can follow design guidelines and create your own good board. There are articles on the Internet about the typical "design rules" that help you create a solid design. Things like proper grounding, use of ground plaves, decoupling of signals between layers, etc. Some of the large tool companies probably have online courses and white papers, too.
A question about communications between micro's. If I need to have a group of modules each with a microcontroller communicating with a master microcontroller( and potentialy up to 15 feet between them), is RS485 a good protocol to use or would one of the others mentioned be better?
The internet is really great for young engineers. I am still in my electronic engineering course and it is sometimes kind of osbolete here in Brazil. But with the internet I am always updated about new technologies and new projects to develop.
slk, I tend to use simple tools to start deciding my troubleshooting approach. It seems to be more intuitive to me by feeling my way around the situation. then go to appropriate test equipment for the detail.
For the archived version of the course presentations can someone scrub the posts? There is a lot of good information from the posts but things like "I have a lot of trouble geting the audio to work", "Use google to open the ppt" and "Hello everyone." take up a lot of space in the post area but don't add anything to the course. They just make it harder to read. Also could the off-ilne/post threads be sorted and placed together? it is kind of hard to follow the thoughts when two or three threads are mixed together.
One advantage of buying development tools from the vendor (e.g. Microchip) is that with the exception of the PicKit 2 or 3, Microchip will replace a broken programmer, ICE or whatever no matter why the tool broke. This support is worth a lot more than the savings buying a knock-off device.
It should be noted that it can be sometimes tricky to program older PIC chips such as PIC16F84 using pickit2/3 which most circuits on the web and in books are based on. Must use the application provided by the programmer rather than through MPLAB.
I'm just getting into microcontrollers and am learning a lot this week. Thanks for the presentations! And the info on some products to start experimentation- Great stuff to know!! Thanks for everything.
@cnorton: A strong pullup means using small value resistor for pull up whereas a weak pullup means using high value resistor for pulling the signal to Vcc. A strong pullup reduces the RC time constant.
post working code on a personal private blog..thatway we can go look at it anytime.. blogs are free from coffee spills.. once my opamp part is working, i post the code; same for pwm, adc, interrupts.. small bit of code for each feature.
From yesterday brief discussion and with more to come in next cycle. Please give your thoughts about quality differences between this level of programming and safety level programming/equipment? What safeguards are there to prevent this type of device (quality) getting used in a larger safety device as a part/piece? Do you think that this is happening? High level there are regulations, etc, but when you get down to this level...is there a problem?
I really miss the Embedded Handbook that Microchip used to print in the "old" days - It was a great reference volume and I referred to it often. Its been probably 6 years or so since the last version was printed.
Jon, great tip about checking the power supply. I learned digital troubleshooting back when measurements were made with volt meters and scopes, no logic probe or analyzer. Power supply voltage and stability was a big deal when begining to troubleshoot or debug. We also learned about voltage characteristics of wounded inputs and outputs.
For those fans of analog-circuit guru Jim Willams, his final work, the book "Analog Circuit Design: A Tutorial Guide to Applications and Solutions," is now in print. The book provides a collection of 41 application notes from Linear Technology Corp. that have stood the test of time and reader interest. The 932-page volume costs about $62 in hardback from Amazon. ISBN: 978-0-12-385185-7. I just got a copy. Excellent reference. --Jon
The audio should start automatically when Alex and I go live by phone in about 45 minutes. If you still have problems, you might have audio blocked by a company firewall--some companies block streaming audio. I'm not a browser expert, so perhaps someone who knows about audio has some ideas for best audio streaming settings. I know the audio for the archived sessions works well here with my Mac and Safari browser. --Jon
@diego88, you will have to go to each topic and under special Education Materials you will find a link called Today's Slide Deck. That will allow you to download it. It is next to the picture of Jon Titus and his info
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