Interesting Atmel Cortex microcontroller families

Communicating with developers of various electronics (both amateurs and professionals), my colleagues and I noticed that the Atmel microcontrollers based on the Cortex-M platform are practically unknown to the general public. I decided to prepare a review of the new families of microcontrollers to show: Atmel is not the only AVR that is interesting.



In the review, I will not list all the families; I will only talk about those that meet one or both criteria:
• unique features of the family;
• the price is better than that of competitors, or comparable (here I have to make a reservation that we are talking about the comparability of wholesale prices).

SAM S and SAM E

These are microcontrollers based on the ARM Cortex-M7 core, which debuted this year with Atmel and ST. The advantages of this core compared to the previous Cortex-M4 are the availability of hardware support for double-precision floating-point calculations (Cortex-M4 has only single precision, and not all Cortex-M4, but only Cortex-M4F), higher performance (DMIPS / MHz is about 1.6 times higher) and a higher CPU clock frequency (up to 300 MHz).

SAM S is the “basic” family, SAM E is the family with Ethernet and CAN on board. Microcontrollers are available in LQFP (64, 100, 144 pins) and LFBGA (100 and 144 pins) packages. Flash memory sizes - from 512 to 2048 KB. All controllers have onboard USB (Host, Device) and an interface for connecting CMOS sensors. In some modifications (depending on the size of the case) there is an external memory interface and an interface for working with memory cards. In addition to these two families, there is also the SAM V family, but these are analogues of the families mentioned above for the automotive industry. You can encounter them only in the debugging kit, common to all families with the Cortex-M7 core.

If we compare these controllers with their ST counterparts, then Atmel favors:
• high clock speed of the CPU (300 MHz vs 216 MHz), which ensures greater performance;
• the presence of chips with memory up to 2048 KB Flash (ST only up to 1024 KB);
• the presence of a family without CAN and Ethernet (which allows you to not overpay for these functions if they are not required in the project).
The advantage of ST controllers is:
• an interface for connecting LCD displays (Atmel recommends using an external memory interface for this);
• the presence of a family without cryptography (Atmel has cryptography on board all microcontrollers).

Atmel microcontrollers do not lose in the price of ST, and therefore aroused great interest among our customers. The microcontrollers of this family retain pin-to-pin compatibility with the "younger" families based on Cortex-M4 (SAM4S and SAM4E). The only pitfall is that this compatibility does not apply to USB pins. This is due to the fact that the USB modules for these families are different: the Cortex-M4 has a USB Device, the flagships have a USB Host and Device.

SAM4L

This is a family of Cortex-M4-based microcontrollers with a clock frequency of 48 MHz and picoPower technology, which ensures low consumption (less than 90 μA / MHz). In terms of performance, this family occupies an intermediate niche between the families STM32 L1 (Cortex-M3, 32 MHz) and STM32 L4 (Cortex-M4, 80 MHz). The prices for these microcontrollers are approximately the same. The set of peripherals is also similar, but SAM4L has two special modules:
1. frequency measurement module;
2. programmable logic module.

The first module allows you to measure the frequency of an external signal by comparing the measured frequency with the reference. The second module allows you to abandon the use of logic circuits on the board (unless of course very complex logic is required). The principle of operation is simple: four inputs make up 16 possible combinations, for each of the combinations the corresponding output state (0 or 1) is set, then the module works without the participation of the CPU according to the given state table. A microcontroller can have one or two of these modules, depending on the case.

SAM G

Another family of low-power Cortex-M4 microcontrollers. From the point of view of the processor, the main difference from the previous family is the availability of a module for floating-point calculations (Cortex-M4F). This family also uses picoPower technology, the consumption is slightly higher than that of SAM4L, but still at a fairly low level (less than 100 μA / MHz).

The family consists of 4 microcontrollers, which differ in flash-memory size (256 or 512 KB), the maximum processor clock speed (from 48 to 120 MHz), and housing sizes (LQFP100 / 64, WLCSP49). A small variety of options for microcontrollers is more than offset by prices that are significantly lower than competitors' prices.

Cortex-m0 +

Powerful productive controllers are, of course, good, but the Cortex-M0 platform nevertheless made a real revolution in the world of microcontrollers. 32-bit microcontrollers confidently crowd out 8-bit controllers not only in performance but also in price. Atmel also launched a number of families on this architecture. A distinctive feature of these families is the SERCOM modules, which, depending on the configuration, can act as UART, SPI, I2C, while it is possible to select the pins that are used by this module. Another feature: the developed PTC hardware module, with which you can create touch interfaces with a large number of controls (buttons, sliders, etc.).

SAM D

This is the base family that underlies all other Cortex-M0 families. If you do not take into account the already mentioned features, this family could be considered quite ordinary: the usual set of peripherals, the usual set of cases, the standard line of memory sizes, the average price on the market.

However, this family deserves mention for two reasons. The first reason is that the senior representatives (SAM D20 and SAM D21) of this family serve as the basis for microcontrollers of other families. SAM D20 has all the features described above atmel'ovsky Cortex-M0 +. SAM D21 is its further development: added USB, DMA, I2S. Between themselves, these pin-to-pin controllers are compatible, have the same line of cases (LQFP32 / 48/64) and flash-memory (from 16 to 256 KB).

The second reason is the recently announced junior representatives: microcontrollers SAM D09, SAM D10, SAM D11. Cases have a small number of conclusions: SOIC14 / SOIC20, QFN24. The possible size of flash memory is 8 or 16 KB. The families themselves are distinguished by a set of available peripherals, while the SAM D11 has a USB Device on board. Prices for small controllers are also small.

SAM L

Of course, the experience gained in creating low-power microcontrollers could not be used for the Cortex-M0 +. This is how the SAM L family came about. A distinctive feature of these microcontrollers is their very low consumption for Cortex-M0 + (less than 35 μA / MHz). There is also a programmable logic module, which is significantly improved compared to the module in SAM 4L. The module allows not only to implement logical operations (AND, NOT, OR, etc.), but also to create more complex logic elements - triggers and latches.

SAM L come in two forms: SAM L21 - low-power microcontrollers with USB, pin-to-pin compatible with SAM D21, and SAM L22 - the same thing, but with an LCD display. Thus, each of the lines is a competitor of the corresponding STM32L0 families: STM32L0x2 and STM32L0x3. SAML21 is already available for order, mass production of SAM L22 is planned early next year. Again, for the price of SAM L21 are comparable to their counterparts from ST.

SAM C

A very interesting family, whose production will begin early next year. From competitors Cortex-M0 + microcontrollers, it is primarily distinguished by the voltage range: 2.7 - 5.5V. Other features are: a frequency meter, LIN interface support, a programmable logic module similar to SAM L.

Two subfamilies are announced:
SAM C20 - pin-to-pin compatible controllers with SAM D20, cases and flash memory size options are also similar.
SAM C21 - backward compatible controllers with SAM C20 (based on pins, memory and peripherals), two CAN controllers are added, a hardware accelerator for dividing and calculating the square root, the temperature sensor is designed as a separate module (and not wound up on the ADC).

Prices are not yet known.

Conclusion

As I hope, this review shows that Atmel is making serious efforts to regain leadership in the microcontroller market. This is expressed both in the tendency to reduce the cost of new families of microcontrollers, and in endowing these families with interesting and sometimes unique functions.

Of course, the merits of each of these families are not limited to what I have called. I did this consciously, so as not to inflate the text and not reduce everything to rewriting parameters from datasheets. Before writing the article, I sketched out a plan from memory, listing those families that seem most interesting to me, and those features of these families that I remember.