Interesting Atmel Cortex microcontroller families

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



In the review, I will not list all the families, I will tell only about those that meet one or both of the criteria:
• unique features of the family;
• the price is better than that of competitors, or comparable (here I have to make a reservation that it is 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 both Atmel and ST. The advantages of this core compared to the previous Cortex-M4 are the availability of hardware support for floating-point double precision (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 higher CPU clock frequency (up to 300 MHz).

SAM S is the “base” family, SAM E is the Ethernet and CAN family on board. Microcontrollers are available in LQFP (64, 100, 144 outputs) and LFBGA (100 and 144 outputs) packages. Flash memory sizes range from 512 to 2048 KB. All controllers have onboard USB (Host, Device) and an interface for connecting CMOS sensors. In some versions (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 previously mentioned families for the automotive industry. You can only encounter them in the debugging kit common to all families with the Cortex-M7 core.

If we compare these controllers with analogues from ST, then in favor of Atmel are:
• a large CPU clock frequency (300 MHz vs 216 MHz), which provides greater performance;
• availability of chips with memory up to 2048 KB Flash (for ST only up to 1024 KB);
• the presence of a family without CAN and Ethernet (which allows not to overpay for these functions, if they are not required in the project).
The advantage of ST controllers is:
• availability of an interface for connecting LCD displays (for Atmel, it is recommended to use an external memory interface for this);
• 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 the Cortex-M4 (SAM4S and SAM4E). The only caveat is that this compatibility does not apply to USB pins. This is due to the fact that the USB modules of these families are different: the Cortex-M4 has a USB Device, and the flagships have a USB Host and Device.

SAM4L

This family of microcontrollers based on the Cortex-M4 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 STM32 L1 (Cortex-M3, 32 MHz) and STM32 L4 (Cortex-M4, 80 MHz) families. The prices for these microcontrollers are about the same. The set of peripherals is also similar, but the SAM4L has two special modules:
1. module frequency measurement;
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 one. The second module eliminates the use of logic chips 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 is set (0 or 1), then the module operates without CPU involvement according to the specified state table. There can be one or two such modules in a microcontroller, 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). In this family, the picoPower technology is also used, the consumption is slightly higher than that of the SAM4L, but still at a fairly low level (less than 100 μA / MHz).

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

Cortex-M0 +

Powerful productive controllers are, of course, good, but the Cortex-M0 platform has made a real revolution in the world of microcontrollers. 32-bit microcontrollers are confidently replacing 8-bit controllers not only with performance, but also with price. Atmel also introduced a number of families to the market on this architecture. A distinctive feature of these families is the SERCOM modules, which, depending on the configuration, can play the role of UART, SPI, I2C, while it is possible to choose the leads that are used by this module. Another feature: an advanced hardware PTC 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 forms the basis of all the 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 members (SAM D20 and SAM D21) of this family serve as the basis for microcontrollers of other families. The SAM D20 has all the atmel's Cortex-M0 + described above. SAM D21 is its further development: added USB, DMA, I2S. Between themselves, these pin-to-pin controllers are compatible, have the same range of enclosures (LQFP32 / 48/64) and flash-memory (from 16 to 256 KB).

The second reason is the recently announced junior representatives: SAM D09, SAM D10, SAM D11 microcontrollers. The enclosures have a small number of pins: SOIC14 / SOIC20, QFN24. 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 an onboard USB Device. Prices for small controllers are also small.

SAM L

Of course, the accumulated experience in creating low-power microcontrollers could not be used for Cortex-M0 +. This is how the SAM L family appeared. The distinguishing 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 of the SAM 4L. The module allows not only to implement logical operations (AND, NOT, OR, etc.), but also to create more complex elements of logic - triggers and latches.

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

SAM C

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

Announced two subfamilies:
SAM C20 - pin-to-pin compatible controllers with the SAM D20, the enclosures and the size of the flash-memory are also similar.
SAM C21 - backward compatible with SAM C20 controllers (by outputs, memory and peripherals), two CAN controllers, a hardware division and square root computing accelerator added, a temperature sensor made as a separate module (rather than an ADC).

Prices are not yet known.

Conclusion

As I hope can be seen from this review, Atmel is making serious efforts to regain its leadership in the microcontroller market. This is expressed as in the trend of cheapening new microcontroller families, and in endowing these families with interesting and sometimes unique functions.

Of course, the advantages of each of the listed families are not limited to what I called. I did it consciously, in order not to inflate the text and not to reduce everything to rewriting the parameters from datasheets. Before writing the article, I sketched a plan from memory, listing those families that seem to me the most interesting, and those features of those families that I remember.