PJRC Teensy 4.1 – Cortex-M7
The Teensy 4.1 is the latest version of the hugely popular development board, wielding an ARM Cortex-M7 processor at 600MHz, with an NXP iMXRT1062 chip, four times more flash memory than its predecessor, and two new locations to add more optional memory. Measuring up at exactly the same size as the Teensy 3.6 (approx. 61mm x 18mm), while providing more I/O capability, the likes of which include an ethernet PHY, SD card socket, and USB host port!
When running at 600 MHz, the Teensy 4.1 consumes approximately 100mA current and provides support for dynamic clock scaling. Unlike traditional microcontrollers, where changing the clock speed causes wrong baud rates and other issues, Teensy 4.1 hardware and Teensyduino’s software support for Arduino timing functions are designed to allow dynamically speed changes. Serial baud rates, audio streaming sample rates, and Arduino functions like delay() and millis(), and Teensyduino’s extensions like IntervalTimer and elapsedMillis, continue to work properly while the CPU changes speed. Teensy 4.1 also provides a power shut off feature. By connecting a pushbutton to the On/Off pin, the 3.3V power supply can be completely disabled by holding the button for five seconds and turned back on by a brief button press. If a coin cell is connected to VBAT, Teensy 4.1’s RTC also continues to keep track of date & time while the power is off. Teensy 4.1 also can also be overclocked, well beyond 600MHz!
The ARM Cortex-M7 brings many powerful CPU features to a true real-time microcontroller platform. The Cortex-M7 is a dual-issue superscaler processor, meaning the M7 can execute two instructions per clock cycle, at 600MHz! Of course, executing two simultaneously depends upon the compiler ordering instructions and registers. Initial benchmarks have shown C++ code compiled by Arduino tends to achieve two instructions about 40% to 50% of the time while performing numerically intensive work using integers and pointers. The Cortex-M7 is the first ARM microcontroller to use branch prediction.
Tightly Coupled Memory is a special feature that allows Cortex-M7 fast single-cycle access to memory using a pair of 64-bit wide buses. The ITCM bus provides a 64-bit path to fetch instructions. The DTCM bus is actually a pair of 32-bit paths, allowing M7 to perform up to two separate memory accesses in the same cycle. These extremely high-speed buses are separate from M7’s main AXI bus, which accesses other memory and peripherals. 512 of memory can be accessed as tightly coupled memory. Teensyduino automatically allocates your Arduino sketch code into ITCM and all non-malloc memory use to the fast DTCM unless you add extra keywords to override the optimized default. Memory not accessed on the tightly coupled buses is optimized for DMA access by peripherals. Because the bulk of M7’s memory access is done on the two tightly coupled buses, powerful DMA-based peripherals have excellent access to the non-TCM memory for highly efficient I/O.
Teensy 4.1’s Cortex-M7 processor includes a floating-point unit (FPU) that supports both 64-bit “double” and 32-bit “float”. With M4’s FPU on Teensy 3.5 & 3.6, and also Atmel SAMD51 chips, the only 32-bit float is hardware accelerated. Any use of double, double functions like log(), sin(), cos() means slow software implemented math. Teensy 4.1 executes all of these with FPU hardware.
What’s the difference between a Teensy 4.0 and 4.1?
- Teensy 4.1 has 8 MB of flash memory for program storage, up from 2 MB
- The microcontroller comes with 1 MB of on-chip RAM which is the same as the 4.0
- The Teensy 4.1 also allows the addition of either or both of two user-supplied extra memories QSPI flash memory and an 8MB PSRAM part
- On the bottom side of the PCB, there are two SOIC-8 footprints for the forementioned memory part options
- A key feature of these additional memories is that they have a dedicated QSPI bus, which doesn’t slow down the Teensy 4.1’s internal program memory
- Teensy 4.1 breaks out the full 16-bit GPIO port (thanks to it’s larger size over the 4.0)
- uSD Card Socket
- 10/100 Mbit Ethernet pins are broken out
- USB port host and Peripheral
- ARM Cortex-M7 at 600MHz
- 1024K RAM (512K is tightly coupled)
- 8 Mbyte Flash (64K reserved for recovery & EEPROM emulation)
- USB Host Port
- 2 chips Plus Program Memory
- 55 Total I/O Pins
- 3 CAN-Bus (1 with CAN FD)
- 2 I2S Digital Audio
- 1 S/PDIF Digital Audio
- 1 SDIO (4 bit) native SD
- 3 SPI, all with 16 word FIFO
- 7 Bottom SMT Pad Signals
- 8 Serial ports
- 32 general-purpose DMA channels
- 35 PWM pins
- 42 Breadboard Friendly I/O
- 18 analog inputs
- Cryptographic Acceleration
- Random Number Generator
- RTC for date/time
- Programmable FlexIO
- Pixel Processing Pipeline
- Peripheral cross triggering
- 10 / 100 Mbit DP83825 PHY (6 pins)
- microSD Card Socket
- Power On/Off management