“Horrible” three-cent MCU - a brief overview of microcontrollers costing less than $ 0.1
I, among others, was amazed at last year's news on the EEVblog blog that some microcontrollers sold for only $ 0.03 apiece. How was that possible? Many have suggested that this is a sale or old remnants. Rummaging through history, I came to the conclusion that there is a whole market segment of super-cheap microcontrollers. Almost all of them are produced by little-known companies from China or Taiwan. In this article, I have summarized the results of my research in this rather unusual niche.
We already know that there is a fairly large range of very powerful microcontrollers costing $ 1.00, but what about the MCU at $ 0.1? Are they “terrible” as they write about them?
How to determine a microcontroller worth $ 0.1? Yes, as you wish; the choice of definition is arbitrary. I decided to go straight, using the cost of 100 pieces in the LCSC store. I found six manufacturers offering one or more chips for less than $ 0.1, all from Asia. If the chips were offered in different packages, I chose the SOP8 option. Some manufacturers had several candidates, so I had to limit myself to choosing typical devices for the final list of 8 candidates.
At large distributors, such as Digikey or Mouser, I did not find microcontrollers for $ 0.1. Obviously, this does not mean that it is impossible to find such MCUs from Western manufacturers - it all depends on the volume of the order. Two factors play a role here: firstly, LCSC works with a much lower margin than large distributors. Secondly, large MCU manufacturers are not dependent on small customers, so they freely set the price for goods purchased in small quantities.
In the absence of programmers and test benches, I was able to review most devices only according to their specifications, with the exception of the Padauk MCU.
In total, I selected eight candidates from six different manufacturers. The summary table is given below.
It has obvious similarities - all devices are designed for battery architecture, and, of course, based on Microchip PIC12. With the exception of MDT, all manufacturers have changed and supplemented their chip circuits. There are probably two reasons: firstly, they wanted to avoid legal problems with Microchip, and secondly, PIC12 has serious limitations. They worked with the main disadvantages - the absence of interruptions, the JMP / CALL address space, switching memory banks and peripherals.
Unfortunately, manufacturers did not share such details as instruction coding or memory algorithms. All development for these devices should go through the IDE from the manufacturers. With the exception of Holtek, all devices depend on a high-voltage programming interface, and they are not so easy to program on site. Only Padauk and Holtek offer devices that can be programmed more than once.
→ Clickable. There is a PDF version
The $ 0.0466 BJ8P509F chip is a slightly improved version of the PIC12C509. The instruction set has been expanded from 12 to 13 bits. This allows you to use jmp with full memory addressing. In addition, added the ability to work with interrupts and an expanded HW-stack.
There is a specification in English, and it is detailed enough to work with the chip. Unfortunately, the manufacturer’s website and IDE is only in Chinese.
Eastsoft Micro has a large portfolio of PIC-based microcontrollers. They call their version of the HR7P RISC architecture. This is a full-fledged battery architecture with interrupt support, an 8-level stack and access to memory and I / O without switching banks .
They have one chip costing up to $ 0.1, and this is HR7P153P45SA. Notable features include 12-bit ADC support, a low-speed oscillator for low power operation, and the addition of two timers with PWM support.
Unfortunately, the website and the specification are only in Chinese.
Holtek is a well-known Taiwan microcontroller manufacturer. Their representative in this category HT68F001 is quite unique: a limited device with 512 words of software flash memory and 16 bytes of RAM. The architecture is very similar to PIC12, synchronized only from the internal 32 kHz oscillator. Since it takes 4 cycles to complete each instruction, it only executes 8000 instructions per second! Apparently, this chip is designed for use in ultra-low power consumption, not demanding on performance.
The chip has excellent documentation. There is a website, a specification, application notes, and an IDE. It is also the only chip with low voltage flash programming capability. All this puts Holtek products apart from the rest.
However, given the limited functionality of this chip, it seems that the ultra-cheap chip segment is not a priority for Holtek.
It is clear that in the chip market up to $ 0.1, Padauk feels right at home. In this price range, they offer dozens of products with a variety of options and types of cases.
All of them are based on the MCU Padauk architecture, which is much more developed compared to PIC12: it uses separate sections of memory for I / O and SRAM, allows addressing to all memory without switching banks. Unlike all other devices, here the stack is in RAM. Most instructions are executed in a single clock cycle.
One interesting and unusual aspect of the Padauk architecture is that it is sharpened for synchronous multithreading, and allows you to run more than one program in parallel on a single MCU core according to the preemptive multitasking scheme. They call this concept "user-programmable processor matrix" (FPPA). A similar concept is used by XMOS in the XCore Architecture . One useful application of multithreading in small MCUs is the creation of virtual peripherals, for example, UART, I 2 C, working in parallel with the main program.
I selected three of their representative products in the SOP8 package: PMS150C, PFS154, and PFS173. They all have one FPPA module, so they do not support multithreading.
PMS150C is the cheapest option, costing $ 0.033, that is, this is the original "three-cent MCU." The device has a one-time programmable memory for 1 kilosword and 64 bytes of RAM. The periphery is represented by many competing options - a 16-bit timer, an 8-bit PWM timer, a low-frequency oscillator, an analog comparator with a 4-bit DAC reference voltage, which can be used to implement the simplest ADC variants. All this is enough to implement the simple functions of the sensor and the control module.
PFS154 costs almost twice as much. However, unlike the PMS150, it has flash memory for 2 kilosheets, it can be programmed many times, which is much more convenient for real development. The periphery is expanded by 3x11 bit PWM modules, which are well suited for controlling RGB LEDs.
Finally, PFS173 further improves the PFS154 chip by adding an 8-bit ADC and expanding flash memory to 3 kiloslov and RAM to 256 bytes.
Padauk provides an IDE for assembly language development and the rather cryptic C (Mini-C) dialect. They have excellent specifications in English and Chinese, as well as a bilingual site. Programming of devices is carried out by a high-voltage protocol for 5 or 6 wires, which makes it difficult to program the chip in place.
A small community has formed around the Padauk MCU on the EEVblog site, trying to create an open source toolkit for their chips. Most of the work is described in this thread .
On August 2019, the engineering analysis of instruction coding was completed, the programming protocol was described, an open programmer was developed, and SDCC integrated support for several PDK architecture options. It is already possible to conduct development for all the mentioned Padauk chips with a fully open toolkit.
Puolop is a Chinese manufacturer of microcontrollers and various mixed analog-to-digital circuits headquartered in Shenzhen. They offer a wide range of chips from Padauk under their brand, in particular, the old OTP versions.
For example, Puolop PTB150CSE looks absolutely identical to Padauk PMS150C. Their cost is slightly less than the original ($ 0.0315 versus $ 0.334). It's unclear what the relationship is between these brands, but Padauk seems to be acting as a supplier to Puolop.
The company’s website and all documentation are only in Chinese. There is no reason to prefer Puolop chips to Padauks chips - save a small fraction of the price.
Yspring Tech is a Chinese company offering a wide range of devices that are functionally comparable to Microchip's competitors. Apparently, most of the assortment was taken from MDT , a Taiwanese company that Yspring either bought or made a partner. Microchip has opposed their business model in the past.
Ysprings adds the MDT10P509 to this review for $ 0.0795. This device appears to be a complete clone of PIC12C509. It may be useful as a cheap replacement for the original, but it is clearly inferior in characteristics to other products in this category.
The MDT10P509 offers 1 kilos of one-time memory, 41 bytes of RAM, and a single 8-bit timer as peripherals. In it, as in the PIC12C509, there are no interruptions, there is only a two-level HW-stack, and the instructions are executed in 4 cycles.
Are these microcontrollers really ugly? Obviously depends on the point of view. They fall into a special category of low-maintenance low-maintenance products with low cost for bulk purchases. Do you need to wait for the button to be pressed and then blink five times with the LED? Do you need a battery operated night light? Chips costing up to $ 0.1 will help you reduce costs and shorten development time.
The catch is that development for most of these devices will be inconvenient due to the limited availability of flash-flashed options and in-circuit programming. Debugging is usually only possible through circuit emulators.
If you enjoy working with low-cost microcontrollers, the Padauk series is without a doubt the best choice. They have the most powerful architecture, a wide range of devices, including options with flash memory, good documentation, and the only line with a set of open tools.
We already know that there is a fairly large range of very powerful microcontrollers costing $ 1.00, but what about the MCU at $ 0.1? Are they “terrible” as they write about them?
Methodology
How to determine a microcontroller worth $ 0.1? Yes, as you wish; the choice of definition is arbitrary. I decided to go straight, using the cost of 100 pieces in the LCSC store. I found six manufacturers offering one or more chips for less than $ 0.1, all from Asia. If the chips were offered in different packages, I chose the SOP8 option. Some manufacturers had several candidates, so I had to limit myself to choosing typical devices for the final list of 8 candidates.
At large distributors, such as Digikey or Mouser, I did not find microcontrollers for $ 0.1. Obviously, this does not mean that it is impossible to find such MCUs from Western manufacturers - it all depends on the volume of the order. Two factors play a role here: firstly, LCSC works with a much lower margin than large distributors. Secondly, large MCU manufacturers are not dependent on small customers, so they freely set the price for goods purchased in small quantities.
In the absence of programmers and test benches, I was able to review most devices only according to their specifications, with the exception of the Padauk MCU.
Overview
In total, I selected eight candidates from six different manufacturers. The summary table is given below.
It has obvious similarities - all devices are designed for battery architecture, and, of course, based on Microchip PIC12. With the exception of MDT, all manufacturers have changed and supplemented their chip circuits. There are probably two reasons: firstly, they wanted to avoid legal problems with Microchip, and secondly, PIC12 has serious limitations. They worked with the main disadvantages - the absence of interruptions, the JMP / CALL address space, switching memory banks and peripherals.
Unfortunately, manufacturers did not share such details as instruction coding or memory algorithms. All development for these devices should go through the IDE from the manufacturers. With the exception of Holtek, all devices depend on a high-voltage programming interface, and they are not so easy to program on site. Only Padauk and Holtek offer devices that can be programmed more than once.
→ Clickable. There is a PDF version
Separate finds
Bojuxing industrial
The $ 0.0466 BJ8P509F chip is a slightly improved version of the PIC12C509. The instruction set has been expanded from 12 to 13 bits. This allows you to use jmp with full memory addressing. In addition, added the ability to work with interrupts and an expanded HW-stack.
There is a specification in English, and it is detailed enough to work with the chip. Unfortunately, the manufacturer’s website and IDE is only in Chinese.
Eastsoft micro
Eastsoft Micro has a large portfolio of PIC-based microcontrollers. They call their version of the HR7P RISC architecture. This is a full-fledged battery architecture with interrupt support, an 8-level stack and access to memory and I / O without switching banks .
They have one chip costing up to $ 0.1, and this is HR7P153P45SA. Notable features include 12-bit ADC support, a low-speed oscillator for low power operation, and the addition of two timers with PWM support.
Unfortunately, the website and the specification are only in Chinese.
Holtek
Holtek is a well-known Taiwan microcontroller manufacturer. Their representative in this category HT68F001 is quite unique: a limited device with 512 words of software flash memory and 16 bytes of RAM. The architecture is very similar to PIC12, synchronized only from the internal 32 kHz oscillator. Since it takes 4 cycles to complete each instruction, it only executes 8000 instructions per second! Apparently, this chip is designed for use in ultra-low power consumption, not demanding on performance.
The chip has excellent documentation. There is a website, a specification, application notes, and an IDE. It is also the only chip with low voltage flash programming capability. All this puts Holtek products apart from the rest.
However, given the limited functionality of this chip, it seems that the ultra-cheap chip segment is not a priority for Holtek.
Padauk
It is clear that in the chip market up to $ 0.1, Padauk feels right at home. In this price range, they offer dozens of products with a variety of options and types of cases.
All of them are based on the MCU Padauk architecture, which is much more developed compared to PIC12: it uses separate sections of memory for I / O and SRAM, allows addressing to all memory without switching banks. Unlike all other devices, here the stack is in RAM. Most instructions are executed in a single clock cycle.
One interesting and unusual aspect of the Padauk architecture is that it is sharpened for synchronous multithreading, and allows you to run more than one program in parallel on a single MCU core according to the preemptive multitasking scheme. They call this concept "user-programmable processor matrix" (FPPA). A similar concept is used by XMOS in the XCore Architecture . One useful application of multithreading in small MCUs is the creation of virtual peripherals, for example, UART, I 2 C, working in parallel with the main program.
I selected three of their representative products in the SOP8 package: PMS150C, PFS154, and PFS173. They all have one FPPA module, so they do not support multithreading.
PMS150C is the cheapest option, costing $ 0.033, that is, this is the original "three-cent MCU." The device has a one-time programmable memory for 1 kilosword and 64 bytes of RAM. The periphery is represented by many competing options - a 16-bit timer, an 8-bit PWM timer, a low-frequency oscillator, an analog comparator with a 4-bit DAC reference voltage, which can be used to implement the simplest ADC variants. All this is enough to implement the simple functions of the sensor and the control module.
PFS154 costs almost twice as much. However, unlike the PMS150, it has flash memory for 2 kilosheets, it can be programmed many times, which is much more convenient for real development. The periphery is expanded by 3x11 bit PWM modules, which are well suited for controlling RGB LEDs.
Finally, PFS173 further improves the PFS154 chip by adding an 8-bit ADC and expanding flash memory to 3 kiloslov and RAM to 256 bytes.
Padauk provides an IDE for assembly language development and the rather cryptic C (Mini-C) dialect. They have excellent specifications in English and Chinese, as well as a bilingual site. Programming of devices is carried out by a high-voltage protocol for 5 or 6 wires, which makes it difficult to program the chip in place.
Open source toolkit
A small community has formed around the Padauk MCU on the EEVblog site, trying to create an open source toolkit for their chips. Most of the work is described in this thread .
On August 2019, the engineering analysis of instruction coding was completed, the programming protocol was described, an open programmer was developed, and SDCC integrated support for several PDK architecture options. It is already possible to conduct development for all the mentioned Padauk chips with a fully open toolkit.
Puolop
Puolop is a Chinese manufacturer of microcontrollers and various mixed analog-to-digital circuits headquartered in Shenzhen. They offer a wide range of chips from Padauk under their brand, in particular, the old OTP versions.
For example, Puolop PTB150CSE looks absolutely identical to Padauk PMS150C. Their cost is slightly less than the original ($ 0.0315 versus $ 0.334). It's unclear what the relationship is between these brands, but Padauk seems to be acting as a supplier to Puolop.
The company’s website and all documentation are only in Chinese. There is no reason to prefer Puolop chips to Padauks chips - save a small fraction of the price.
Yspring Tech / MDT
Yspring Tech is a Chinese company offering a wide range of devices that are functionally comparable to Microchip's competitors. Apparently, most of the assortment was taken from MDT , a Taiwanese company that Yspring either bought or made a partner. Microchip has opposed their business model in the past.
Ysprings adds the MDT10P509 to this review for $ 0.0795. This device appears to be a complete clone of PIC12C509. It may be useful as a cheap replacement for the original, but it is clearly inferior in characteristics to other products in this category.
The MDT10P509 offers 1 kilos of one-time memory, 41 bytes of RAM, and a single 8-bit timer as peripherals. In it, as in the PIC12C509, there are no interruptions, there is only a two-level HW-stack, and the instructions are executed in 4 cycles.
Conclusion
Are these microcontrollers really ugly? Obviously depends on the point of view. They fall into a special category of low-maintenance low-maintenance products with low cost for bulk purchases. Do you need to wait for the button to be pressed and then blink five times with the LED? Do you need a battery operated night light? Chips costing up to $ 0.1 will help you reduce costs and shorten development time.
The catch is that development for most of these devices will be inconvenient due to the limited availability of flash-flashed options and in-circuit programming. Debugging is usually only possible through circuit emulators.
If you enjoy working with low-cost microcontrollers, the Padauk series is without a doubt the best choice. They have the most powerful architecture, a wide range of devices, including options with flash memory, good documentation, and the only line with a set of open tools.
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