Author Topic: 8-bit uC - is there even a point?  (Read 27575 times)

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Online mikeselectricstuff

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Re: 8-bit uC - is there even a point?
« Reply #250 on: October 04, 2018, 07:13:46 am »
PIC24 series is every bit as easy to use as 8 bit but you get vastly better chip.

I don't understand the lack of love for that series.

I somewhat arbitrarily chose Atmel a number of years ago. It was partly based on the size and depth of information available on the internet at the time. After getting setup and dialed in for most of the basic functions I needed - I had no real interest in learning another product family - even if it was 'better'

Now, I am at a place where I am ready for more power, better peripherals, better everything. I have emotionally prepared myself for a learning curve to get that.

and if you are going to upgrade and have a learning curve why go half way and pick 16bit from a single source when
you can go all the way to 32 bit and have numerous similar choices from many sources
There is almost no difference between the PIC24 and PIC32 range from the C programming user's point of view so it's not a big curve - many of the peripherals are the same or at least back-compatible supersets on the PIC32, so code written for the PIC24 will often need minimal changes to run on the 32
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Offline JPortici

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Re: 8-bit uC - is there even a point?
« Reply #251 on: October 04, 2018, 07:21:55 am »
PIC24 series is every bit as easy to use as 8 bit but you get vastly better chip.

I don't understand the lack of love for that series.

I somewhat arbitrarily chose Atmel a number of years ago. It was partly based on the size and depth of information available on the internet at the time. After getting setup and dialed in for most of the basic functions I needed - I had no real interest in learning another product family - even if it was 'better'

Now, I am at a place where I am ready for more power, better peripherals, better everything. I have emotionally prepared myself for a learning curve to get that.

and if you are going to upgrade and have a learning curve why go half way and pick 16bit from a single source when
you can go all the way to 32 bit and have numerous similar choices from many sources

because arm microcontroller from different manufacturers (sources) are notoriously pin-to-pin compatible  :palm:
or if you are talking about upgrade paths, microchip has offered pin-to-pin (or almost pin to pin) upgrades since the dawn of mankind
 

Offline JPortici

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Re: 8-bit uC - is there even a point?
« Reply #252 on: October 04, 2018, 07:24:44 am »
PIC24 series is every bit as easy to use as 8 bit but you get vastly better chip.

I don't understand the lack of love for that series.

(Early) PIC24 had lot of quirks, even in newer models the peripherals are dumb, low MIPS anyway. PIC18 K42/K83 series have far better peripherals
if you want 16bit go dsPIC.
 

Offline technix

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Re: 8-bit uC - is there even a point?
« Reply #253 on: October 04, 2018, 09:05:07 am »
Using a 32bit ARM micro means you'll very likely be using a peripheral library, and they're usually shit to work with.
Just when you start to learn the library they release a new version and it breaks everything.
You can live without the library and you can be better off without it, but it will take some additional brain power to understand the registers. When vendors are given gigabytes of address space to place control registers, they tend to get lazy and verbose.
 

Online coppice

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Re: 8-bit uC - is there even a point?
« Reply #254 on: October 04, 2018, 09:12:07 am »
Using a 32bit ARM micro means you'll very likely be using a peripheral library, and they're usually shit to work with.
Just when you start to learn the library they release a new version and it breaks everything.
You can live without the library and you can be better off without it, but it will take some additional brain power to understand the registers. When vendors are given gigabytes of address space to place control registers, they tend to get lazy and verbose.
It seldom takes much brain power. It takes time. Often lots of it. Often patching together information from various sources, because no one source is complete. Often using the source code for the crappy library, because only the programmer of that library ever figured out some details that are not in the documentation.
 

Offline Howardlong

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Re: 8-bit uC - is there even a point?
« Reply #255 on: October 04, 2018, 09:25:27 am »
PIC24 series is every bit as easy to use as 8 bit but you get vastly better chip.

I don't understand the lack of love for that series.

(Early) PIC24 had lot of quirks, even in newer models the peripherals are dumb, low MIPS anyway. PIC18 K42/K83 series have far better peripherals
if you want 16bit go dsPIC.

I think it depends on application. I'm quite a fan of the PIC24FxxKA/KL/KM devices, with wide supply voltage ranges, low power consumption and plenty of peripherals that make them well suited to small battery powered devices. You can forego voltage regulators for example in single Li cell applications.

dsPIC33 are all 3.3v parts and not very low power.

For real low power in energy harvesting, the newer PIC16(L)F1xxxx and some other manufacturers' devices fare even better in current consumption than PIC24FxxKA/KL/KM in most representative like for like comparisons, but those PIC24Fs have significantly more processing oomph than PIC16 which may be beneficial in a given application.

Sometimes the peripherals and features are a decision maker: I switched from using a PIC24F16KM202 down to a PIC16F1619 because of the PIC16F161X's math accelerator/PID controller peripheral and higher current FET driver pins, producing an even cheaper design in the process, but it was a close run thing.

As always, the devil's in the details!
 

Offline technix

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Re: 8-bit uC - is there even a point?
« Reply #256 on: October 04, 2018, 10:59:03 am »
Using a 32bit ARM micro means you'll very likely be using a peripheral library, and they're usually shit to work with.
Just when you start to learn the library they release a new version and it breaks everything.
You can live without the library and you can be better off without it, but it will take some additional brain power to understand the registers. When vendors are given gigabytes of address space to place control registers, they tend to get lazy and verbose.
It seldom takes much brain power. It takes time. Often lots of it. Often patching together information from various sources, because no one source is complete. Often using the source code for the crappy library, because only the programmer of that library ever figured out some details that are not in the documentation.
What I mean is reading through the chip’s manual and have a general grasp on what goes where and does what, and how the modules are associated with each other. This will take some brainpower to build up the dependency map. When coming to individual peripherals spend some time poking around it to figure out what does what, and with those understandings you can start writing your own drivers.

I had the unfortunate of having a project almost get killed by the sheer bloat of STM32CubeMX. Overcame it by skipping the libraries and cook up my own drivers.
 

Offline JPortici

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Re: 8-bit uC - is there even a point?
« Reply #257 on: October 04, 2018, 12:44:22 pm »
dsPIC33 are all 3.3v parts and not very low power.

dsPIC33EV is a 5V part, i use it in a lot of projects.. It needs 2 to 5 jumpers (depending on how may pins you are willing to sacrifice) to make it compatible with PIC18s, if you care about that.
But that doesn't matter, most new projects are going to be dsPIC33CH. sweet sweet dual core

About the PIC24 (KA)... I may still have PTSD, they were my very first 16bitter in high school and to this day i still have problems with them. And they are really "dumb" compared to the newer 8bitters, as you saw yourself.
Sure you have a core that's easier to deal with but the peripherals are just meh (to me)
« Last Edit: October 04, 2018, 01:06:09 pm by JPortici »
 

Offline Howardlong

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Re: 8-bit uC - is there even a point?
« Reply #258 on: October 04, 2018, 03:50:41 pm »
dsPIC33 are all 3.3v parts and not very low power.

dsPIC33EV is a 5V part, i use it in a lot of projects.. It needs 2 to 5 jumpers (depending on how may pins you are willing to sacrifice) to make it compatible with PIC18s, if you care about that.
But that doesn't matter, most new projects are going to be dsPIC33CH. sweet sweet dual core

About the PIC24 (KA)... I may still have PTSD, they were my very first 16bitter in high school and to this day i still have problems with them. And they are really "dumb" compared to the newer 8bitters, as you saw yourself.
Sure you have a core that's easier to deal with but the peripherals are just meh (to me)

Yes, you're right there a 5V parts too, but they need voltage regulators too, my point was around the additional BOM requirements for that: in single cell Li devices, you can forego that with these PIC24FxxKA/KL/KM devices. I regularly use the KM devices which are pretty well set up with peripherals, both analogue and digital. If you need to do a bit of number crunching, they are a reasonable solution, PIC16s are almost all weak in that area. A bonus was differential ADC, and dual DAC with external outputs: there are plenty of use cases for that dual output DAC, and no many microcontrollers offer them, especially with external outputs. I had discounted the PIC16 as I didn't think it would have the number crunching horse power, but with the PID accelerator my view changed. The math accelerator is a real PITA to learn how to use though!
 

Offline technix

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Re: 8-bit uC - is there even a point?
« Reply #259 on: October 04, 2018, 06:22:00 pm »
dsPIC33 are all 3.3v parts and not very low power.

dsPIC33EV is a 5V part, i use it in a lot of projects.. It needs 2 to 5 jumpers (depending on how may pins you are willing to sacrifice) to make it compatible with PIC18s, if you care about that.
But that doesn't matter, most new projects are going to be dsPIC33CH. sweet sweet dual core

About the PIC24 (KA)... I may still have PTSD, they were my very first 16bitter in high school and to this day i still have problems with them. And they are really "dumb" compared to the newer 8bitters, as you saw yourself.
Sure you have a core that's easier to deal with but the peripherals are just meh (to me)

Yes, you're right there a 5V parts too, but they need voltage regulators too, my point was around the additional BOM requirements for that: in single cell Li devices, you can forego that with these PIC24FxxKA/KL/KM devices. I regularly use the KM devices which are pretty well set up with peripherals, both analogue and digital. If you need to do a bit of number crunching, they are a reasonable solution, PIC16s are almost all weak in that area. A bonus was differential ADC, and dual DAC with external outputs: there are plenty of use cases for that dual output DAC, and no many microcontrollers offer them, especially with external outputs. I had discounted the PIC16 as I didn't think it would have the number crunching horse power, but with the PID accelerator my view changed. The math accelerator is a real PITA to learn how to use though!
Single cell Li-po and 3.3V parts... That is a pain to design. So far my best bet is actually abusing a battery bank chip TP5410 into pushing out 4.7V regardless whether the power is connected or not (by default it switches the output off when external power is applied) then regulate it down to 3.3V using AMS1117, SPX3819 or TPS52200. I am not completely sure about those buck-boost chips and their current capability.
 

Offline SiliconWizard

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Re: 8-bit uC - is there even a point?
« Reply #260 on: October 04, 2018, 06:41:28 pm »
Single cell Li-po and 3.3V parts... That is a pain to design.

Yeah. I usually try and select parts that work down to 3V or below, and regulate the battery to this voltage with an LDO. (If you don't need your main 3V as a reference, you may even not regulate it at all, but in this case you have to use parts that can handle up to 4.2V, and 3.3V parts usually can't operate at above 3.6V, so that severly limits your options.) Most of my battery-operated designs are powered at 3V or even lower (if I can), such as 2.7V or 2.5V. So no need for a step-up regulator, which has two drawbacks: reduced efficiency obviously (especially at low currents) and a current draw on the battery that increases as the battery empties - which is often bad for the battery's life and may even damage it if not protected properly.

 

Offline westfw

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Re: 8-bit uC - is there even a point?
« Reply #261 on: October 04, 2018, 11:04:39 pm »
Quote
I don't understand the lack of love for that series [PIC24]
I think that in general, 16bit microcontrollers didn't get a lot of traction because the first "resource" that people were running out of was memory - either program memory or flash memory.  And the 16bit chips tended to have the same sorts of memory sizes and awkward bank switching schemes as the 8bit chips.  The sort of 256k/64k flash/ram configurations you can commonly get for cheap with a 32bit CPU is practically unheard of in the 8bit world (and somewhat unpleasant to use if you can find it.)
("because kids today write bloated code with bloated libraries to implemented bloated GUIs.   I remember when WordStar and MINCE would ...")
 

Online maginnovision

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Re: 8-bit uC - is there even a point?
« Reply #262 on: October 04, 2018, 11:14:48 pm »
I used an avr8 with extra 128k sram to get 256k/64k(120k)rom/ram and with the XMM I/F it was completely transparent other than extra cycle to read/write to it.
 

Offline technix

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Re: 8-bit uC - is there even a point?
« Reply #263 on: October 05, 2018, 02:21:58 am »
Single cell Li-po and 3.3V parts... That is a pain to design.

Yeah. I usually try and select parts that work down to 3V or below, and regulate the battery to this voltage with an LDO. (If you don't need your main 3V as a reference, you may even not regulate it at all, but in this case you have to use parts that can handle up to 4.2V, and 3.3V parts usually can't operate at above 3.6V, so that severly limits your options.) Most of my battery-operated designs are powered at 3V or even lower (if I can), such as 2.7V or 2.5V. So no need for a step-up regulator, which has two drawbacks: reduced efficiency obviously (especially at low currents) and a current draw on the battery that increases as the battery empties - which is often bad for the battery's life and may even damage it if not protected properly.
The battery bank chipset I used comes with both a linear charger (similar to TP4056) and a fixed 5V step-up regulator in one SOIC8-1EP package, I just need to give it a charge current control resistor, a power inductor and a Schottky diode to make it all work. It is rated for 1A maximum output current.
 

Offline Howardlong

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Re: 8-bit uC - is there even a point?
« Reply #264 on: October 05, 2018, 01:01:49 pm »
Single cell Li-po and 3.3V parts... That is a pain to design. So far my best bet is actually abusing a battery bank chip TP5410 into pushing out 4.7V regardless whether the power is connected or not (by default it switches the output off when external power is applied) then regulate it down to 3.3V using AMS1117, SPX3819 or TPS52200. I am not completely sure about those buck-boost chips and their current capability.

This was actually one of my applications: use the PIC as a switch mode charge regulator and low current power supply, as there wasn't a single device off the shelf that did what I wanted: gas gauge, charger, power supply. Having a device with a reasonably wide voltage range (2.0 to 5.5V for PIC24FV, 2.3 to 5.5V for PIC16F1xxx well suited to 5V (USB) Li charging, and running off the Li battery without external regulators. It did mean external MOSFETs though. The PIC16F161x has a pair of 100mA drive outputs, useful in lieu of gate drivers. I use a Cuk topology to allow an output voltage higher or lower than the Li source.
 

Offline Fungus

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Re: 8-bit uC - is there even a point?
« Reply #265 on: October 05, 2018, 01:37:49 pm »
So my question is - what are 8-bit uC still used for (in new designs).

Anything that runs off 5V.

As a hobbyst, is there still a point in using them

Of course. It's not all about price. 8 bits is still overkill for many, many jobs and can really simplify life.
 

Offline technix

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Re: 8-bit uC - is there even a point?
« Reply #266 on: October 05, 2018, 03:11:33 pm »
This was actually one of my applications: use the PIC as a switch mode charge regulator and low current power supply, as there wasn't a single device off the shelf that did what I wanted: gas gauge, charger, power supply. Having a device with a reasonably wide voltage range (2.0 to 5.5V for PIC24FV, 2.3 to 5.5V for PIC16F1xxx well suited to 5V (USB) Li charging, and running off the Li battery without external regulators. It did mean external MOSFETs though. The PIC16F161x has a pair of 100mA drive outputs, useful in lieu of gate drivers. I use a Cuk topology to allow an output voltage higher or lower than the Li source.
TP5410 is a combo charger and power supply, the only thing missing would be the gas gauge. That chip is actually a bit wasteful as it is a linear charger and a fixed 5V output non-synchronous boost converter combo, but for low cost applications there is little other options than TP5410 + resistor + inductor + two diodes.

Attached is the board photo of that power section: the SO-8 chip in the middle is TP5410, that and a few components around it makes the 3.3V power delivery section. The Li-po is on the back of the board. The input voltage to the AMS1117 is 4.V for USB power and 5V for battery power.
 

Offline GeorgeOfTheJungle

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Re: 8-bit uC - is there even a point?
« Reply #267 on: October 05, 2018, 04:55:30 pm »
Of course. It's not all about price. 8 bits is still overkill for many, many jobs and can really simplify life.

And 4 bits better yet...
http://brave.com <- THE BEST BROWSER
 

Online coppice

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Re: 8-bit uC - is there even a point?
« Reply #268 on: October 05, 2018, 05:37:53 pm »
Of course. It's not all about price. 8 bits is still overkill for many, many jobs and can really simplify life.
And 4 bits better yet...
4 bitters aren't so easy to get outside Japan these days.
 

Offline Fungus

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Re: 8-bit uC - is there even a point?
« Reply #269 on: October 05, 2018, 07:06:47 pm »
Of course. It's not all about price. 8 bits is still overkill for many, many jobs and can really simplify life.

And 4 bits better yet...

If it's enough, then, sure...

I don't know of many 4 bit chips though. Even the tiniest uC are 8 bits these days.

eg. https://www.microchip.com/wwwproducts/en/ATtiny4

 

Offline legacy

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Re: 8-bit uC - is there even a point?
« Reply #270 on: October 05, 2018, 08:06:04 pm »
16bit ... 68HC16 ... never seen, never used  :-//
 

Online coppice

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Re: 8-bit uC - is there even a point?
« Reply #271 on: October 05, 2018, 08:33:55 pm »
16bit ... 68HC16 ... never seen, never used  :-//
Motorola developed two cores - the CPU16 (the core in the 68HC16) and the CPU32 (based on the 68000 core) - at the same time, intending to mix and match a set of modular peripherals and these two cores to suit a wide range of needs. It turned out most people were either OK with Motorola's existing HC05/HC08 or HC11 cores, or needed the performance of the CPU32.
 

Offline langwadt

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Re: 8-bit uC - is there even a point?
« Reply #272 on: October 05, 2018, 09:00:22 pm »
16bit ... 68HC16 ... never seen, never used  :-//
Motorola developed two cores - the CPU16 (the core in the 68HC16) and the CPU32 (based on the 68000 core) - at the same time, intending to mix and match a set of modular peripherals and these two cores to suit a wide range of needs. It turned out most people were either OK with Motorola's existing HC05/HC08 or HC11 cores, or needed the performance of the CPU32.

they also have (had?) the coldfire which was also ~68k and the m.core which afair was very similar what ARM became with cortex and thumb2
 

Offline chickenHeadKnob

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Re: 8-bit uC - is there even a point?
« Reply #273 on: October 05, 2018, 09:04:39 pm »
Anything that runs off 5V.

Turning that around and looking at starting requirements from the other end of the telescope, what if you want true 5V outputs and not just 5V tolerant and must have 32 bit core?
I know of:
  Cypress PSOC4 arm cortex m0
  Cypress PSOC5 arm cortex m3
  Atmel/Microchip SAMC20 and 21     automotive series cortex m0+ these  additionally are one of the few mcu that have CAN FD

Are there any others? including obscure non-arm 32 bitters?

Quote from: coppice
Motorola developed two cores - the CPU16 (the core in the 68HC16) and the CPU32 (based on the 68000 core) - at the same time, intending to mix and match a set of modular peripherals and these two cores to suit a wide range of needs. It turned out most people were either OK with Motorola's existing HC05/HC08 or HC11 cores, or needed the performance of the CPU32.

moto HC05. Yuck. Any youngling that still yearns for the 8 bit era should be forced, as I was, to program these register starved memory deficient craptastic things. That will cure you.
« Last Edit: October 05, 2018, 09:28:14 pm by chickenHeadKnob »
 

Online coppice

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Re: 8-bit uC - is there even a point?
« Reply #274 on: October 05, 2018, 09:12:38 pm »
Quote from: coppice
Motorola developed two cores - the CPU16 (the core in the 68HC16) and the CPU32 (based on the 68000 core) - at the same time, intending to mix and match a set of modular peripherals and these two cores to suit a wide range of needs. It turned out most people were either OK with Motorola's existing HC05/HC08 or HC11 cores, or needed the performance of the CPU32.
moto HC05. Yuck. Any youngling that still yearns for the 8 bit era should be forced, as I was, to program these register starved memory deficient craptastic things. That will cure you.
The HC05 was one of the most successful MCU families. It was a key part of what made Motorola the biggest MCU maker in the world.
 


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