Migrating from PIC18 to ARM: which MCU to choose?
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From: Stimpy on 21 Jul 2010 17:44 We have a product based around the PIC18F6680 which is now becoming a rare and expensive part. Since it looks like ARM devices are winning the popularity war, the chips are cheap and plentiful. The question is, with so many vendors and parts to choose from which one should we go with? The main requirements for this application, in order of importance, are: 1) availability - having devices in stock at Digikey/Mouser is almost a necessity since we can't wait 12 weeks for backordered parts from some distributor; two weeks is probably the maximum 2) price - since our original PIC18 is now at $9.47 each (qty 100) pretty much any device that comes in under this price will be better 3) 64K FLASH - since ARM code is more compact than PIC18 this should be more than enough 4) 4K RAM 5) 128 bytes EEPROM 6) CAN controller 7) timers with 1 output compare and 2 input captures 8) SPI 9) 2 UARTs 10) 8-bit DAC (or PWM) 11) a DMA controller that works with the SPI would be nice but not essential 12) two comparators 13) 10-bit ADC 14) under 0.2 mA when stopped Processing speed and power consumption aren't too critical. I've given up trying to find built-in comparators on any ARM device so I guess those will have to be external from now on. Low standby current is important, but I can always cut power to the whole device if required. I've found one (LPC2364) that has a built-in DAC but those seem to be rare. The only ones I've found with built-in EEPROM are the LPC2927/ LPC2929. I also can't decide between ARM7, ARM9, Cortex-M0 and Cortex- M3. Right now Cortex-M3 appears to be more popular and the three leading choices are: Texas Instruments - Stellaris NXP - LPC series ST - STM32 series Given the above criteria there are still dozens of devices to choose from that would fit most of the requirements. NXP seems to have the best pricing; other than that I'm lost. Any suggestions or are there any other choices that I've overlooked?
From: linnix on 21 Jul 2010 19:34 On Jul 21, 2:44 pm, Stimpy <rjmvxlvzj...(a)mailinator.com> wrote: > We have a product based around the PIC18F6680 which is now becoming a > rare and expensive part. Since it looks like ARM devices are winning > the popularity war, the chips are cheap and plentiful. The question > is, with so many vendors and parts to choose from which one should we > go with? The main requirements for this application, in order of > importance, are: > > 1) availability - having devices in stock at Digikey/Mouser is almost > a necessity since we can't wait 12 weeks for backordered parts from > some distributor; two weeks is probably the maximum > 2) price - since our original PIC18 is now at $9.47 each (qty 100) > pretty much any device that comes in under this price will be better > 3) 64K FLASH - since ARM code is more compact than PIC18 this should > be more than enough > 4) 4K RAM > 5) 128 bytes EEPROM > 6) CAN controller > 7) timers with 1 output compare and 2 input captures > 8) SPI > 9) 2 UARTs > 10) 8-bit DAC (or PWM) > 11) a DMA controller that works with the SPI would be nice but not > essential > 12) two comparators > 13) 10-bit ADC > 14) under 0.2 mA when stopped > > Processing speed and power consumption aren't too critical. I've given > up trying to find built-in comparators on any ARM device That's less of a problem. > so I guess > those will have to be external from now on. Low standby current is > important, but I can always cut power to the whole device if required. > I've found one (LPC2364) that has a built-in DAC but those seem to be > rare. The only ones I've found with built-in EEPROM That's more of a problem. > ... > Any suggestions or are there any other choices that I've overlooked? My suggestion (except for EEPROM): The LM3S2110 microcontroller is based on the ARM Cortex-M3 controller core operating at 25 MHz, with 64 kB single-cycle flash, 16 kB single- cycle SRAM, CAN controller, Systick timer, three 32-bit or six 16-bit general purpose timers, watchdog timer, SSI / SPI controller, I2C interfaces, three analog comparators, UART, two motion-control Pulse Width Modulation (PWM) outputs, low drop-out voltage regulator, brown- out reset, power-on reset controller, and up to 40 GPIOs.
From: -jg on 21 Jul 2010 22:11 On Jul 22, 9:44 am, Stimpy <rjmvxlvzj...(a)mailinator.com> wrote: > Any suggestions or are there any other choices that I've overlooked? Try Cypress PSoC5, which does have Comparator choices, and also EEPROM. Cypress are frustratingly slow at releasing prices, but they do show CY8CKIT-014 PSoC® 5 FirstTouch Starter Kit $49 in stock. Freescale have announced a M4 version, sampling soon www.freescale.com/kinetis - but data is thin right now. Or, I see the new Nuvoton series, have just flipped into Stock, at Nu Horizons http://www.nuvoton.com/hq/enu/ProductAndSales/ProductLines/IndustrialIC/ARMMicrocontroller/ARMCortexTMM0/Pages/default.aspx NUC100LE3AN NUVOTON 128KF 16KR QFP48 $2.5250 NUC100RE3AN NUVOTON 128KF 16KR QFP64 $2.7875 NUC120LE3AN NUVOTON 128KF 16KR QFP48 USB $2.7875 NUC120RE3AN NUVOTON 128KF 16KR QFP64 USB $2.9625 NUC120VD2AN NUVOTON 64KF 8KR QFO100 USB $2.7875 These are 5V (wide supply range), and I see they do have Analog Comparators too :) Eval PCBs look well priced too... NUMICRO-SDK NUVOTON TECH CORP AMERICA Development Tools $43.7500 NUTINY-SDK-120 NUVOTON TECH CORP AMERICA Development Tools $19.0000 Signs of a product manager, who knows what they are doing ? -jg
From: Chris Burrows on 21 Jul 2010 22:37 "Stimpy" <rjmvxlvzjqwi(a)mailinator.com> wrote in message news:7b290caa-37fe-4f99-a278-9fb63a7def07(a)j8g2000yqd.googlegroups.com... > The only ones I've found with built-in EEPROM are the LPC2927/ > LPC2929. Depending on how you are planning to use the EEPROM you might not need to let that restrict your choices. With the NXP LPCxxxx MCUs you can use IAP (In Application programming) to write to unused flash from within your program. If you only need 64K flash for your code you'll have more than enough left over to use for other purposes. That should give you many more devices to choose from. If you are frequently writing a few bytes to various locations in EEPROM then IAP might not be suitable. However, if your updates are infrequent or you are just storing a block of data at the end of a run to be used at the start of the next run it might be a feasible solution. The Cortex-M3 LPC1xxx devices are relatively new and haven't yet gone through the usual spate of revisions - OK if you like a sense of adventure. If you are a more conservative type the more stable LPC2xxx ARM7 series should be more to your taste. Regards, Chris Burrows CFB Software Astrobe: LPC2xxx Oberon-07 Development System http://www.astrobe.com
From: Michael Kellett on 22 Jul 2010 03:02
"Stimpy" <rjmvxlvzjqwi(a)mailinator.com> wrote in message news:7b290caa-37fe-4f99-a278-9fb63a7def07(a)j8g2000yqd.googlegroups.com... > We have a product based around the PIC18F6680 which is now becoming a > rare and expensive part. Since it looks like ARM devices are winning > the popularity war, the chips are cheap and plentiful. The question > is, with so many vendors and parts to choose from which one should we > go with? The main requirements for this application, in order of > importance, are: > > 1) availability - having devices in stock at Digikey/Mouser is almost > a necessity since we can't wait 12 weeks for backordered parts from > some distributor; two weeks is probably the maximum > 2) price - since our original PIC18 is now at $9.47 each (qty 100) > pretty much any device that comes in under this price will be better > 3) 64K FLASH - since ARM code is more compact than PIC18 this should > be more than enough > 4) 4K RAM > 5) 128 bytes EEPROM > 6) CAN controller > 7) timers with 1 output compare and 2 input captures > 8) SPI > 9) 2 UARTs > 10) 8-bit DAC (or PWM) > 11) a DMA controller that works with the SPI would be nice but not > essential > 12) two comparators > 13) 10-bit ADC > 14) under 0.2 mA when stopped > > Processing speed and power consumption aren't too critical. I've given > up trying to find built-in comparators on any ARM device so I guess > those will have to be external from now on. Low standby current is > important, but I can always cut power to the whole device if required. > I've found one (LPC2364) that has a built-in DAC but those seem to be > rare. The only ones I've found with built-in EEPROM are the LPC2927/ > LPC2929. I also can't decide between ARM7, ARM9, Cortex-M0 and Cortex- > M3. Right now Cortex-M3 appears to be more popular and the three > leading choices are: > Texas Instruments - Stellaris > NXP - LPC series > ST - STM32 series > Given the above criteria there are still dozens of devices to choose > from that would fit most of the requirements. NXP seems to have the > best pricing; other than that I'm lost. > Any suggestions or are there any other choices that I've overlooked? Apart from leadtimes I think ST are a good bet - this is based on good experience with the STM32 range of parts. I have not used the NXP parts or looked at them in very great detail. The good things about the STM32s: big range of parts with good footprint compatibility and good peripherals, tick all your boxes except EEPROM. Be very careful with any supplier about availability - if you don't have the parts in your stores don't count on them being in stock. ST and others have parts on 1 year leadtimes so desperate users will buy up all the distributor stock if they can. Michael Kellett |