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 moving to another microcontroller family: experiences? 
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Joined: Fri Jul 18, 2014 2:52 am
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Hello,

I have some experience with the MSP430 for several years now, although most of my experience has been on the schematic side of things. I'll try to put my comments in the numbered list based on the first post...

1. The MPS430 series is a 16 bit family of microcontrollers which spans from 8 pin to 128 pin devices. Their peripheral set has a fair quantity of built-in interfaces that you would expect: UART, SPI, I2C, several channel ADC, DAC, PWM, etc. and some even have a USB interface. They won't beat a 32 bit processor in performance and with a maximum speed of about 25 MHz in the family, they aren't the fasted products out there. That said, their hardware multiplier, very low power modes and other features make them very useful (IMO) in most microcontroller applications. Few 16 bit microcontrollers can consume <100 uA/MHz during active (non-sleep) mode like the FRAM based MSP430s can.
2. I can't say much about the interrupt subsystem but there is a fixed priority list for the interrupt sources so program knowing the interrupt priorities.
9. The prices are pretty decent in low quantities. The MSP430F5259IZQE, for example, is less than $7 in quantity of 1 and includes 128K FLASH, 32K RAM, 12ch ADC, 53 DIO, 32 bit hardware multiplier and eight independent serial ports. That part is available now and the parts we use where I work have never had an availability problem over the ~6 years that I have been designing with them.
10. The MSP430 family has been pretty popular and I expect that they will continue to grow and advance with new technologies. Examples of their advancement are recent additions of a USB interface series and an FRAM memory based series. They also continue to sell their low cost and low end parts for around a dollar in quantity of 1.

Any additions or corrections to what I wrote are welcome.

Chris


Fri Jul 18, 2014 4:46 am
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Welcome, Chris -- nice to have you with us!

FWIW, I too am a '430 fan, having used it for three or four projects. It's a chip which is a pleasure to program in assembly language, thanks to the plentiful registers and well-thought-out addressing modes.

-- Jeff

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Fri Jul 18, 2014 12:06 pm
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A little bragging about those close to me and my wife:
Chris is an EE who lives near us. He has been working on itty-bitty satellites for the last 10+ years. Since I work at home for an employer that's 1200 miles away, I have had almost no recent personal contact with EEs, making my acquaintance with Chris all the more valuable. I met him through a very special "niece" of ours-- actually the sister of our daughter-in-law, and she calls me "Uncle Garth," nearly making me levitate off the floor. She's a mechanical engineer, a project manager at a company that makes absolutely huge compressors, some even having to be disassembled to get them on a truck. It would have been nice to know him before I had to compete with her for his time. :lol: Her sister is our daughter-in-law who is a professional programmer.

Chris, I thought you also emailed or PM'ed me about the TI µCs, but I can't for the life of me find it now. Did I imagine it? Anyway, if you've read the whole topic, you know some of the problems I've had with TI over the last 25+ years; but if I take the MSP430 route, I have an additional support person now! :D

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Last edited by Garth on Mon Jun 22, 2015 4:32 am, edited 1 time in total.



Fri Jul 18, 2014 7:16 pm
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I will also say that I have had very good luck with the MSP430. Just a few thoughts:

The MSP430 is great for low-power stuff, which is what it was designed for. I don't know if that makes a difference to you, Garth. Apart from the overall ease of use and the excellent forum community, that is the only real advantage I see over the ARM family. Even power efficiency is not always a deciding factor now that companies like EFM32 (now Silabs) are producing lower power ARMs. You may want to consider whether you really want and have the time to learn two instructions sets and two peripheral systems. An MSP430 can outgrow a project and need an ARM but an ARM project will never become an MSP430 project.

Brad R wrote:
Anyhow, when you have a program that requires 16K of ROM, figure you'll need 32K of ROM on an ARM chip
Have you tested this? I don't have numbers to prove it but we got to talking about this on IRC one day and it seems that ARM Cortex M0 and MSP430 code are often roughly the same size.

Chris wrote:
their hardware multiplier, very low power modes and other features make them very useful
The hardware multiplier was not part of the original chip and was later grafted on as a peripheral. This means that you have to disable interrupts for a few cycles then load values into a memory mapped register, like you would for a UART. Many ARMs (even the $2 ones) can multiply in a single-cycle.

Make sure to check out the FRAM series of MSP430s as well. Instead of having flash the entire RAM is non-volatile.

In general, the MSP430 is easy to use and has a great community which is why I have stuck with it, but if you can overcome the scariness of ARMs, it might be a better option going forward.


Fri Aug 01, 2014 4:09 pm
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Druzyek wrote:
Have you tested this?


No, I'm working on that now. :) That was just a general observation based on instruction word size.

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Fri Aug 01, 2014 4:31 pm
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There are some good considerations there. So far I have never needed anything ultra-low power, but I have no idea whether that will change. Disabling interrupts for a multiplication may be a problem. FRAM making it like all the memory is non-volatile RAM though sounds attractive. I have not had to pull the trigger yet, so I'll keep collecting info for now.

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Fri Aug 01, 2014 9:16 pm
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Garth wrote:
Disabling interrupts for a multiplication may be a problem.

I'm pretty sure this doesn't apply unless your ISR might also attempt to use the multiplier -- is that what you meant, Druzyek? (BTW, welcome!)

cheers,
Jeff

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Sat Aug 02, 2014 2:59 am
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Quote:
I'm pretty sure this doesn't apply unless your ISR might also attempt to use the multiplier -- is that what you meant, Druzyek? (BTW, welcome!)

I haven't used any chips that have one myself but you can find more details here: http://www.ti.com/lit/an/slaa042/slaa042.pdf

It does say: "The loading of registers Operand1 (MPY, MPYS and MAC) and Operand2
must not be separated by an interrupt while using the multiplier."

You will probably be fine not using the hardware multiplier since MSP430s don't usually do a lot of heavy lifting anyway.


Sat Aug 02, 2014 5:23 pm
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Druzyek wrote:
you can find more details here
Cool, thanks -- an app note specifically about the multiplier! I didn't realize it also featured a Multiply-Accumulate function.

The caveat about disabling interrupts typically doesn't apply, although Section 3.2 does address the atypical case of using the multiplier both in the foreground and the background.

Druzyek wrote:
In general, the MSP430 is easy to use and has a great community which is why I have stuck with it
I too have had positive experiences with the '340. I found coding in assembly to be productive and enjoyable. It doesn't take many lines of code to get things done, thanks to plenty of 16-bit registers and a deceptively powerful set of addressing modes. Of course the 340's low-power aspect may sometimes be valuable, but it's a mistake to suppose this low-power CPU has crippled programming capabilities.

cheers,
Jeff

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Sat Aug 02, 2014 6:38 pm
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Jeff, 340 for 430?

So far the only thing I have needed a really fast multiply for is timer-based, interrupt-driven direct digital synthesis of analog signals, AKA a phase accumulator, and setting the output amplitude for each sample, in the ISR itself, rather than having separate wave tables for all different amplitues you might want. So for that, I should not be concerned about interrupts having to be disabled for the multiply (since they normally are disabled in the ISR anyway). I have not had the muliply performance to do this so far, but now I would like to be able to.

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Sat Aug 02, 2014 7:24 pm
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Hi Garth,

Forgive me for reviving such an old thread.

May I ask which PIC device you were using for the project you were working on back in May 2014 when your started this thread, please?

Cheerful regards, Mike


Mon Jun 22, 2015 3:11 am
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PIC16F74 and '72. The project used both simultaneously.

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Mon Jun 22, 2015 4:22 am
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Mike, K8LH wrote:
Forgive me for reviving such an old thread.

Don't apologize. There's a reason the archives are kept, and sometimes picking up the discussion in the same place again prevents wasted repetition and cluttering the forum. I sometimes go through years-old material and remind myself of some good stuff that's still just as true. (I also find typos in things I wrote years ago, and I correct those, or I find links that have gone dead and need to be updated, or find that it's appropriate to add a new link for others who will come along later and read the archives.) Projects on a forum like this may go years, and related discussions should too.

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Mon Jun 22, 2015 4:39 am
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Garth wrote:
The very little I've heard about Atmel's AVRs sounds good, but according to Dave Jones in his EEVBlog, Atmel is not in as good of a financial situation to survive in the long term. I don't want this to be a self-fulfilling prophecy though. Daryl Rictor on the 6502.org forum has spoken well of AVRs, and there have cursed PICs.

I'm not sure exactly what "there have cursed PICs" was supposed to say [Edit: maybe "and many there have cursed PICs"]; but anyway, interestingly, tonight as I was going to Microchip's website to check out their offerings in serial data converters, I got the message that Microchip was acquiring Atmel:
http://www.microchip.com/announcements/ ... ires-atmel

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Sat Feb 20, 2016 4:34 am
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