MICROCONTROLLERS

ET-WEB51 TCP/IP Ethernet Web Control Board

2008-02-13T14:32:36Z

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Connecting Two UARTs?

2007-11-08T04:26:07Z

I have a project which consists of a pair of microcontrollers (PIC16F877A and PIC16F777 to be exact). These function as a unit, with one being the "master" and the other a "slave". They respond to commands sent on a serial port. Electronically they're hooked up with the input going to the master CPU's UART input pin, so it can receive commands and act on them. The master CPU's UART output pin is connected directly to the slave CPU's UART input pin so that it can send commands on to it when necessary.

Unfortunately, it looks like the slave isn't waiting for input on its UART. I'm guessing that it's seeing noise (and thus endless framing errors) on the line, confusing it. So now I'm not sure if the master's properly driving it when not explicitly sending a byte or something.

So in a setup like this, do I need to have a pull-up or pull-down resistor on the serial line between the CPUs or something?

                 ___________       ___________
        |\      |   CPU 1   |     |   CPU 2   |
        | \     |           |     |           |
Input --|  >----| UART IN   |  ?  |           |
        | /     |  UART OUT |-----| UART IN   |
        |/      |___________|     |___________|
      RS-485
     Receiver

Any hints would be appreciated. Thanks!
Crossposted to electronics and microcontroller

ETA: Solution was found. Thanks to all the suggestions from people here! Actually, it turned out I had the hardware and configuration bits all correct, but just needed to refine the timing a little bit. It turns out that to use the USART, you SET the TRIS bits for both serial pins. Then when you turn on the serial port, it takes over management of the pins, tri-stating the TX line when the serial transmitter is disabled, and driving the output (in spite of TRISC) when the transmitter is enabled.

It also turned out that I didn't need a pull-up or -down resistor, at least in this case. Once I got the timing right, so that the master CPU's transmitter was on and driving the line way before the slave CPU's receiver was turned on and listening, everything worked out just fine.

I'm looking for a bit of guidance on choosing a microcontroller.

2007-08-05T17:35:39Z

Overview: To light my water cooling rig with a color corresponding to the water temperature.

The main reservoir in my water cooling system has an acrylic top and bottom. The bottom section has a predrilled whole meant for an LED. My plan is to mount either a dual color LED(red, blue) in this hole. Or drill a second whole and mount 2(again red, blue). Also I will be adding a thermosistor(or some other temp sensor band-gap, etc.) to the loop for temperature sensing.
I would like to have some kind of microcontroller/basic stamp/RISC CPU+Dog watch the thermosistor value(or some kind of interpreter hooked up to the thermosistor) and vary the intensity of the two LED's accordingly. So when the system detects say a temperature of 30C and below only the Blue LED will be lite. But once 35C or more is reached it should slowly add in the red LED while dialing down the blue LED until say 50C. At which point I would like the red LED to be fully lit. I would imagine through the use of 2 PWM channels or output to some kind of external PWM controller. The system will run off the computers powersupply as 12, 5, and 3.3 volts are all readily available.

I have some future projects planned that will also require microcontrollers(or perhaps a full on PC).
Briefly these include:

1) A lighting controller for my workstation(comp. desk)
Required functionality: No fewer than 4 PWM channels for controlling high wattage transistors(preferably more, many more). Aswell as a few channels for running Running relays. No less than 12 independent I/O channels.

2) A realtime/logging AC power consumption meter similar to these Link Link.
Required functionality: Monitor an AC shunt(s) value. Display watt usage as well as projected usage over various time periods via a small LCD display. Log usage over time of a connected AC load.

3) A full home heating and cooling system based on long term thermal storage.
Required functionality: Polling of multiple temp. sensor, flow meters, and power shunts. be able to trip relays for pumps, and perform long term data storage of all system values.

My technical background includes 2 years of electronics in highschool 10 years ago. Along with some programming courses in college(basic, pascal, C++). I'm good for Ohm's law and not much else. But I have an absurd amount of free time coming up here shortly and wouldn't mind getting in way over my head.

So the question is a simple one.
Which microcontroller family/models should I be looking into meet my current and future project goals while keeping in mind this the first time I have ever attempted anything like this? PIC? AMTEL? Motorola?

OOpic vs Basic Stamp

2007-01-29T20:40:05Z

Hi, I'm new here and don't do the microcontroller thing too often but am driven by task to get back into it :}

I worked with the Stamp some years ago on a "real time" servo controller. Now I need to build a small process control system. I was ready to dust off my old Basic Stamp notes and buy some toys when I found the OOpic. It does have a couple pluses over the Stamp, mostly the virtual-circuits multitasking feature. But besides that I'm still very biased toward the Stamp. There's more ready made parts/boards/gadgets for it, I already own some of the gear and I'm familiar with the Stamp. And I hate judging from appearences, but the OOpic site is not too great (is the English in the manuals like that of the site?)

I already know what all you awesome assembly gurus will say to all this Basic stuff :} But does anyone have OOpic vs Stamp experience? Hopefully this doesn't start a big micro-war, I just want to know if the "multitasking" is worth switching over for. Thanks for any help!

www.parallaxinc.com
www.oopic.com

Microcontroller choices

2006-08-23T13:03:50Z

I've been away from the microcontroller world for quite some time now. The last thing I built was around a Motorola 6805...yeah, that long. I realize that what I'm about to ask is mostly a personal choice, a lot like asking "who is better, Santa or the Easter Bunny?", but I'll ask anyway...

Let's pretend you've been away from microcontrollers a really long time. You now need to whip up something that involves controlling a (still) camera and needs fairly accurate timing. You also need to drive a small (128 x 128 or so) lcd (not with live video or photos or anything like that, just time and status and stuff like that). It would be nice if it were fairly cheap to develop on, and thrifty on batteries too. What would you use?

I've been looking at a couple of things, but I'll not mention them yet in order to not taint your answers.

Transceivers, Cell Phones, and RS-232.

2006-06-05T05:10:06Z

Transceivers, Cell Phones, and RS-232. Ok, here is my situation, I would like to have my computer communicate large distances to a Microcontroller. I can find simple RS-232 transceivers that will get the job done, but will only communicate a distance of 20 Meters. I found one company that www.maxstream.com that sells RS-232 RF modems that can go up to 30 miles (if you have an extreme antenna). But I would like to communicate with my MCU device over greater distances. Perhaps 100 miles, but it is within a cell site. I don’t mind using a cell phone, but I don’t know how. Could anyone help me out here?

help help

2006-03-18T15:37:16Z

do anybody have any experience with tms320 series dsp? im interested in pcb designing,layout guidlines for this dsp.

thnks.

74.4094 headaches

2005-12-20T07:14:23Z

Not directly microcontroller-related, but I figure there are more people who use 74HCT4094 shift registers in their microcontroller projects.

I have a 'train' of three 74HCT4094 shift registers, that I drive with a PIC 16F628A. I use two of the three shift registers to drive two 7 segment displays -- with the decimal point, that makes for 8 leads. The displays are common anode, so the shift registers have to sink the current from the segments. (The third shift register is for driving something else, which has not been hooked up yet.)
The circuit consists of a PIC driving the shift register train. The strobe lines of all three shift registers are tied together and to a pin of the PIC. The same is the case with the output enable and clock lines. Pin 9 of a shift register is tied to the data line of the next shift register, so that the data will, indeed, shift from one register to the next. The first shift register's data pin is fed directly from the PIC.

To test the circuit, I clock in 1's and 0's alternatingly -- 16 bits in all.

When there is only a shift register in the first socket, it all works as expected: half of the segments is lit up, the other half is off. But when I place a second shift register in the second socket, all segments of both displays all light up -- as if only 0's have been clocked in. This also happens when I leave the second socket empty and place a shift register in the third socket.
When I measure the voltage on, say, the OE pin, I get an even voltage across all the three sockets, so it seems unlikely to me that the extra shift register dips one of the lines below the threshold.

Can anyone help me fix this problem? I'm on a deadline (it's for a christmas present for my dad), and I have been trying to get it to work for four days now...
If you need more information or a clarification, please don't hesitate to comment and ask!

EDIT: I got it to work by driving the second shift register from the PIC and feed its output to the first shift register. There is no reason why it would not work the other way around, but I'm not complaining.

EDIT PART THE SECOND: And now it is broken again... I undid all the changes I made to the circuit, but that didn't help either.

Me again

2005-11-24T10:03:25Z

Hi all,
Thanks for the responses to the last question, I think I know what I need to do now.

Basically the outputs I have to read will be logic 1 or logic 0 I believe.

The options I was looking at were:
1. build a microcontroller based device
2. get a data acquisition device from National Instruments or Labjack or something like that
3. connect directly to a serial port

Are these valid options?

spare me, I'm a newbie

2005-11-17T12:09:40Z

Hi,
I'm a database and gui programmer mainly.
I've been given a requirement as follows:
The client will output 3 alarms to 3 binary switches.
I need to trap changes to the switches and update a database with what switch changed and what state it changed to.
I'd planned using a microcontroller which the switches would input to and which would output to a PC (via RS232 or preferably USB).
I'm getting conflicting accounts of how long it would take to build such a device (1 week to 1 month). I've been playing with a Microchip picKit Flash starter kit for a day or so.
What I want to know is if there's readily available commercial units that would do what I'm looking for or could be customised quiet easily or failing that how long would it take for someone who knew what they were doing to build this?
We'll only need a dozen or so of them.
Are there any resources on the net which might help me?
TIA

PCB cad

2005-09-16T23:52:26Z

Just a quick non-microcontroller question. I'm looking for a good free/shareware PCB drafting program, what do you guys use?

microcontroller @ 2005-09-07T14:36:00

2005-09-07T19:48:32Z

the traction control is working (with a few minor bugs)!

which now leads me to my next project... or sort of a continuation. i think i'm going to build an electronic ignition controller. its tough to do because an engine is very sensetive to spark advance and retard. especially a turbocharged engine. i hope i dont break anything.

but i'm moving so all projects are on hold for a couple weeks. why move to new jersey? because its better than oklahoma.

oh, does anyone know where i can pick up some cheap servo motors?

PIC programming/IC-Prog problems

2005-09-04T06:36:56Z

Hi folks,
I'm mostly a newbie getting back into microcontrollers. I've done a good deal of low-level hobbying on the BASIC Stamp BS2p-40, and I even once got this PIC-16F84A working more than a year ago (and only that once), but I've forgotten quite a bit about PICs specifically, and now that I'm back into it, I can't get certain things to work, and they're difficult things to search for online - I've tried to no avail.

I'm using the Olimex PG2C, the LED of which I have seen in the past light up when programming/verifying/erasing/etc. It wasn't doing it this time around, and I recall that it wasn't about 6 months ago when I made a half-hearted effort to get back into it. Another problem is that IC-Prog always finds that there's a programmer, even when it's unplugged, and it always writes/verifies/erases with no errors, even if I remove the PIC from the ZIF socket. After much tweaking of settings the other night, I got the LED to blink when I was verifying, and then taking the PIC out, it errored, as it should. I figured it was solved, and moved onto reacquainting myself with the programming and wiring knowledge. I got through enough of that, made a HEX sample, and then it all fell apart again. When I try to load the HEX into IC-Prog, the title bar changes to the path and file, but the hex data doesn't update. The entire program code area remains filled with 3FFF blocks. I've read everything I can find - the entire help file end-to-end, lots of online things and old forum posts. I'm pretty sure I have things set up right - COM 2, PIC 16F84A, all the configuration bits, the HEX file matches the tutorials, JDM programmer with Windows API as recommended by Olimex, etc. It all seems right. Anyone know why the hex data doesn't reflect the file contents, or should it? Maybe that area is only supposed to show the chip's data? I seem to recall this has always been a problem, even when I got the PIC programmed that one time - I just let it program despite the 3FFFs, and the chip worked. BTW, I did try that, and nothing - the PIC seems dead. I've also tried a new, and unused 16F84A - nothin'.

When I attempt to program any '84A, it does the same thing - the Olimex LED does nothing while IC-Prog runs through its progress bars with no problems, and sings the songs of a succesful programming at the end. I have the verify programming boxes, and none of the communication inversion boxes checked, but they aren't noticing that I'm successfully programming an empty programmer. Without IC-Prog's help, I'm kinda stuck right now for getting anything accomplished. I've even updated to the latest version and tried that - no dice. I'm hoping someone's been here and knows a way out, because I don't want to lose faith and give up on microcontrollers again.

Thanks!

Update: Looks like it was my hex file after all. It matched number for number with the sample from "Easy Microcontrol'n" by David Benson, but it's quite a few years old now, and may be too out-of-date. IC-Prog was the real stopping point in the pipeline, but dropping in some randomly-found hex code from a midi sequencer project I found via Google worked beautifully, clearing up all errors. Maybe with some more debugging I'll be able to find exactly what it was that had IC-Prog doing nothing at all with my hex. Thanks all, for the help!

Stair Lights

2005-09-03T20:57:36Z

Microcontroller stair lights??? why not?

BACKGROUND

These lights were inspired by my cat. We have an older cat, and with old age comes a loss of agility, coordination and night sight. At night when the house lights are off I had heard the cat trip on the stairs to the basement. I needed to come up with a method of lighting the stairs at night when the house is dark. I thought that I could install a night light that comes on when it is dark. But this would have been too easy, there must be a more complex way to aid the cat. The end result is my microcontroller controlled stair lights. There is a laser beam at the top and bottom of the stairs, the height of the beams allows it to detect humans as well as our cat. There is an LED installed under each stair tread, this softly lights each stair.

OPERATION

When a beam is broken the lights ramp on, it might look as though they just turn on but there is a soft start algorithm that brings them from off to on quite quickly. There is then a delay to allow the person/animal to use the stairs. The lights then turn off one stair at a time following the person/animal. For example if the top beam was broken to activate the lights the lights will turn off starting with the top stair light. The lights ramp off at a slower more noticeable rate. There is also a small speaker that is connected to the system, the purpose was to be alerted if a small child was attempting to go upstairs. This speaker was mainly used while doing debugging, it has since been padded way down so that it is barely audible since it is not needed. Two buttons on the unit were going to be used to program the device and force the lights on or off. These have not completely been programmed since there has never been an occasion to need them.

(there are mutliple videos showing this hella cool project off at the link. No this was not my project. I wish.)

microcontroller @ 2005-08-10T14:58:00

2005-08-10T20:08:58Z

wow. i started this community a while ago... i thought no one would ever join it.

well, since ive been in oklahoma in training for the air force for about 7 months i havent had any time to play with my micros. until now. my latest project- traction control for my car. i'm using a silabs c8051f350 http://www.silabs.com/public/documents/tpub_doc/dshort/Microcontrollers/Precision_Mixed-Signal/en/C8051F350_Short.pdf

my program measures the revolutions of the drive wheels and the non-driven wheels. if the difference reaches a certain level (indicating a certain amount of tire slip) it cuts engine spark momentarilly to keep the tires from spinning beyond a rate that can be controlled. the cool part? i have a little dial on the dashboard that i can adjust the amount of traction. there is still some bugs though. i'm at the library right now so i dont have the program but i'll see if i can bring it over on my cool new USB jumpdrive.

thanks for keepin it alive, guys

bit manipulation, 180 degree turn

2005-08-07T23:11:24Z

I just have to mention this to someone who'd understand, posting in my own journal would get a bunch of blank stares from my friends...
I've been working on the Atmel AT91R40008 (ARM7) for the past 6+ months and am finally switching back to some unfinished AVR projects... I guess I'd forgotten that the mindset for single-bit port manipulation is completely different! On the AVR, definitions for the individual IO pins is given by their bit number, eg: PB7 (Port B, Bit Number 7) is defined as #define PB7 7. On the ARM, however, they're defined by the value of the bit number, eg: P7 (General Purpose I/O pin 7) is defined as #define P7 0x80. So, configuring multiple pins on the ARM is standard C-style bit-manipulation, which at first really frustrated me after having been able to individually control bits with a single instruction on the AVR... For instance, if I wanted to turn on P7, P8, and P9 on an ARM all in the same instruction, I could essentially say setportpins(P7 | P8 | P9);. So with that mindset driven into me for the past 6 months I proceded to do the following on my AVR code: PORTB = PB3 | PB4 | PB5... Took me a minute to figure out the flaw in this technique ;)

Recomendations

2005-08-03T13:13:49Z

I'm currently beginning working on an UAV(Underwater Autonomous Vehicle) robotics project.

In the past I've always used Basic Stamps, however I'm beginning to wonder if perhaps PIC microcontrollers aren't a bit more economical and well supported.

The biggest problem I have however (Aside from making the gargantuan leap from regular robotics to underwater robotics, what with all the water proofing). Is I know no one personally that uses PIC microcontrollers, so I can't get a good feel for them.

So, does anyone have any opinions on the Basic vs PIC MCs?

16F84 serial

2005-07-25T03:47:27Z

YES. I'm so excited. I'm new to programing pics, just got back into it. Assembled a 16F84 to output ascii A through a single pin, serially. I know this isn't too hard, and there are already programs out there to do it, and more advanced pics with uarts, but now I can do it myself. Since none of my friends care or know what the hell i'm talking about, i decided to post it here...

"large integer implicitly truncated to unsigned type"

2005-05-14T19:55:48Z

Hi all, I've been having this weird warning for some time, and I've just been ignoring it because it works. But I was wondering if any of you had an idea. The warning is at the following line:

LED_disp((uint8_t)LED_R);

LED_R is defined as:
#define LED_R ((uint8_t)(1<<7))

to signify that I want LED_R to be the seventh bit (10000000 in binary). The odd thing is it only complains about LED_R. LED_(A-G) are almost identical in code:

#define LED_G (uint8_t)(1<<6)
...
LED_disp(LED_G)

LED_disp() is defined as follows:
#define LED_disp(value) \
({ \
((uint8_t)PORTB) = ~((uint8_t)(value)); \
((uint8_t)LED_value) = ((uint8_t)(value)); \
})

Everything works without a hitch, but LED_R is the only one that gives a warning. I only added the extra typecast and additional parentheses in an effort to try to alleviate this warning, to no avail.

It looks as though it's not accepting (1<<7) as an unsigned 8-bit integer, dispite all my typecasts...
Ideas? Thanks!

microcontroller @ 2005-04-03T13:48:00

2005-04-03T20:51:43Z

hey,

I am a student taking a microcomputer systems (assembly) class, and I need some help understand a few things. We are using the TI MSP430 microcontroller and I have the following question which I can't answer (note: these are not for a lab report or for homework, we actually don't have a book or homework and that is what is making this class so difficult).

So...

Which files are "cleaned" after the "make clean" command?

Which ones are "made" after the "make" command.

Why those files and not other ones?

What's the difference between asm_lst and obj_lst file?

What generates them?

What's the .x file?

Multiple Serial Lines

2005-04-03T05:04:05Z

I'm curious of exactly how one gets multiple serial lines to go into one port. That is, if it is even possible.

Basically, I have 3 serial devices that I hope to connect to a computer. The thing is, I'm sending it over an RF rs-232 line.

Any ideas?

picotux

2005-03-29T20:30:44Z

The picotux module: containing an ARM7 CPU, a network port and a serial port -- running Linux. Think of the projects you could suddenly net-enable with this: getting data from the network, doing heavy-duty processing on the 55MHz picotux module, and pushing commands out via the serial port to (a chain of) microcontrollers...

It's a bit pricey for the hobbyist (99 euros!), but I'd love to get my mitts on one to toy around with.

PEBKAC

2005-02-02T04:32:00Z

Well, after some idea of browsing websites--all of which were good, thank you--I have come to the following conclusions:

I am in WAY over my head.
I have no idea what I need in order to start working on this project.
I am an idiot. Definite PEBKAC.

So I'm just going to ask the last few questions I have, and perhaps someone can refer me to a TFM (of T many FMs) which I can then perform the R operation on.

fub Suggested the Microchip PICs. I've also seen things about the AVRs from some of you. I checked out GPUTILS, and I think I'll stick with a PIC until I actually know what I'm talking about.

However, I don't own anything usable to program a Microcontroller beyond a bunch of PCs with serial ports.

Am I looking for a programmer and then just chips in packages, then hooking up flash memory to go with them, and building my own solution, or can I get something more like an OOPic, or an Acroname Brainstem which basically has "everything" included on a single PCB?

I would assume that what I want for development is probably one of those PCB's--but how do I identify that vs. just the chip (e.g.) 28-pin DIP packages?

I'm sure I've probably answered my own question, but...something's just not clicking.

Also, I'm thinking that anything we do would probably have some method of "respecting our client's freedom" --as RMS puts it--and in addition to seeing the code we'd probably also want to make it easy for them to put any new code on the devices themselves. I'm not sure how that'd be done with just the chip package.

Second stupid question

2005-01-13T02:36:15Z

Here's one. Since I have some ideas from my last post about _what_ MC to buy, the second question is _where?_

I've had some luck with DigiKey (but it's a bit of the ol' information overload as it's tuned to the person who really knows what they are looking for) and Acroname (where I bought my OOPic but I'm not interested in Robotics as much with this project)...

Anyway, I'm looking for a few other reputable places you swear by when you have to order a part online.

Thanks in advance,
--Benanov

assembly is fun!

2004-12-11T17:18:26Z

::points shotgun at computer::