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:: EPE Chat Zone ­:: ­Radio Bygones Message Board :: » EPE Forum Archives 2007-2009 » Archive through 18 June, 2007 » New thread « Previous Next »

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riki
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Username: riki

Post Number: 68
Registered: 10-2005

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Posted on Wednesday, 06 June, 2007 - 11:59 am:   Edit Post Delete Post Print Post    Move Post (Moderator/Admin Only)

Sri,still learning to navigate the CZ.Getting old and getting forgetfull.In last year taught myself C (MCC18) for PIC18f series and now find I am forgetting my assembler skills.

Correction to my last posting - should read 'Devantech'. And also not forgetting 'JELU'.

I think twice now before designing anything from scratch.

Regards,
RG
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obiwan
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Username: obiwan

Post Number: 1761
Registered: 12-2005

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Posted on Wednesday, 06 June, 2007 - 04:14 pm:   Edit Post Delete Post Print Post    Move Post (Moderator/Admin Only)

Always good to think at least twice before doing anything from total scratch.

To keep both of your programming skills up to date, you should think about using assembler code snipits in your C code.

Most good assemblers should have a function for using in-line assembly.
Do Not Hit The Fly That Lands On The Tigers Head.
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john_becker
:::: Super User ::::
Username: john_becker

Post Number: 1414
Registered: 05-2005

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Posted on Wednesday, 06 June, 2007 - 06:16 pm:   Edit Post Delete Post Print Post    Move Post (Moderator/Admin Only)

Indeed, and beware of ever taking time off from what you know. I did that around 18 months ago, stopped PIC designing for 6 months. Then it took quite a while once I restarted to get back into the swing of it. But it's back :-)

J
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riki
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Username: riki

Post Number: 69
Registered: 10-2005

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Posted on Wednesday, 06 June, 2007 - 06:52 pm:   Edit Post Delete Post Print Post    Move Post (Moderator/Admin Only)

How refreshing to get responsive feedback on this CZ.Other CZ's seem to have a one way system as though (clue) I'm talking double-dutch!.

While were here discussing C compilers.I have tried in vain to get a free PIC16 C compiler.Microchip's Website doesn't seem to have any.

I have used the CC5x Knudson compiler with a 1K program limit.Compiled and stripped out the ASM source code and then continued in asssembler,but this is not very good.

Also had a quick look @ BoostC but this also has a 2K limit and I left it alone since would have to learn a whole new bag of syntax.

What I have been trying to do is to rewrite some of my old ASM projects (mostly PIC16F84 )using C -a good way to learn C.But the way it's going I shall probably abandon all the PIC12/16/17's in favour of the PIC18F.

Covered most of the hardware peripherals including interrupts,PWM and UART and Timers,but have yet to get my head around SPI.

Is SPI a fast syncronous comms facility.? Cos if I need very fast serial comms usually with the PC I use FTDI's USB/serial bridges in DLL mode.and can spit out > 1Mbits/second.Still to build a receiver capable of capturing and saving this amount of information.

Regards,
Rg
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riki
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Username: riki

Post Number: 70
Registered: 10-2005

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Posted on Wednesday, 06 June, 2007 - 06:58 pm:   Edit Post Delete Post Print Post    Move Post (Moderator/Admin Only)

Nearly Forgot.Also had a look @ C using Microelektronica, but found that that the C functions were buried in the 'Monitors ROM' and inaccessible!.So couldn't pinch any of their routines - maybe that's the idea which is a shame really for learning purposes.I'll have another go tonite and see how far I get.

Regards
RG
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grab
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Username: grab

Post Number: 497
Registered: 05-2005


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Posted on Thursday, 07 June, 2007 - 10:09 am:   Edit Post Delete Post Print Post    Move Post (Moderator/Admin Only)

http://sdcc.sourceforge.net/

I've not used it myself, but several people on here have and say it's OK.

Yeah, SPI is synchronous comms - the master device puts out a clock and some enable lines, and the slaves either read or write data on the clock edges. It can be very fast, but having a clock means it's fundamentally limited by the connection. SPI is very widely used for internal links between devices on a PCB at fairly high bitrates, but you wouldn't really want to use it on a long cable between the PC and your equipment. For one thing the link might not be very reliable as capacitance and inductance kill your square wave, and for another thing you're going to be effectively setting up an aerial radiating 1MHz (or whatever bitrate). For high data rate stuff, USB is probably the way to do it these days.

Graham.
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eagre
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Username: eagre

Post Number: 148
Registered: 05-2005


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Posted on Friday, 08 June, 2007 - 02:05 am:   Edit Post Delete Post Print Post    Move Post (Moderator/Admin Only)

Synchronous protocols such as SPI and I2C do require a separate clock line (no problem in most MCU applications) and can have limited line distances (depending on transmission line characteristics). However, they do have high data rates. RS-232 (synchronous or asynchronous) was developed years ago for devices like teletypes (remember them). With its +-12V signal levels and current detection it is very tolerant of long, bad lines but has very limited data rates. It is a (widely accepted) dinosaur. However, many devices require this protocol.

There are many designs, using chips such as the MAX232, for converting between a MCU's 0 - 5V levels and RS-232 levels. However, if the communication is between a MCU and a PC, it should be noted that most PCs, and USB/Serial adapters, will accept 0 - 5V input and often put out at most +- 5V serial output. All that is necessary at the MCU is a current-limiting resistor on output and a voltage divider, plus Schottky diode from ground (if you doubt the MCU's internal diodes) on input. In my experiance it works like a charm. I will admit that I have used such conversion methods on only three PCs and two USB/serial converters.

Ed

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