Teensy 4.1 地表上最快的開發板 600MHz的ARM Cortex-M7處理器

描述

Teensy 4.1 地表上最快的開發板 600MHz的ARM Cortex-M7處理器

Teensy 4.1是最新一代非常受歡迎的開發平台，搭載了600MHz的ARM Cortex-M7處理器和NXP iMXRT1062晶片，比4.0多了四倍的Flash記憶體，還可選擇在兩個新的位置上增加更多記憶體。Teensy 4.1與Teensy 3.6的尺寸和形狀相同（2.4英寸×0.7英寸），提供更強大的I/O能力，包括以太網PHY、SD卡插槽和USB主機埠。

在運行600 MHz時，Teensy 4.1消耗約100mA的電流，並提供支援動態時脈調節。與傳統微控制器不同的是，在改變時脈頻率時，會導致波特率等問題，但Teensy 4.1硬體和Teensyduino的軟體支援Arduino定時功能，允許動態速度變化。串列波特率、音頻流采樣率、Arduino函數如delay()和millis()以及Teensyduino的擴展，如IntervalTimer和elapsedMillis，在CPU改變速度時仍然可以正常工作。此外，Teensy 4.1還提供了一個關機功能。通過將按鈕連接到On/Off引腳，可以通過長按按鈕5秒完全關閉3.3V電源，並通過簡短的按鈕壓住開啟。如果連接了硬幣電池到VBAT，Teensy 4.1的RTC在關閉電源時仍然可以繼續跟踪日期和時間。Teensy 4.1還可以超頻，超過600MHz！

ARM Cortex-M7為真正的即時微控制器平台帶來了許多強大的CPU功能。Cortex-M7是一款雙發射超級標量處理器，意味著M7可以在每個時鐘周期內執行兩個指令，運行速度高達600MHz！當然，同時執行兩個指令取決於編譯器對指令和寄存器的排序。最初的基準測試顯示，由Arduino編譯的C++代碼在使用整數和指針進行數值密集型工作時，通常可以達到兩個指令的40%到50%。Cortex-M7是第一個使用分支預測的ARM微控制器。在M4上，循環和其他必須分支的代碼需要三個時鐘週期。在M7上，循環執行幾次後，分支預測將消除這種開銷，使分支指令僅運行一個時鐘週期。

緊密耦合記憶體(Tightly Coupled Memory)是Cortex-M7的一個特殊功能，使用一對64位元寬的匯流排，讓M7能夠以單個週期快速地存取記憶體。ITCM匯流排提供64位元的路徑以擷取指令。DTCM匯流排則是一對32位元的路徑，允許M7在同一個週期內進行多達兩個分離的存取。這些極高速的匯流排是分開的，與M7的主要AXI匯流排(存取其他記憶體和周邊裝置)不同。512的記憶體可以被當作緊密耦合記憶體存取。Teensyduino會自動將你的Arduino程式碼分配到ITCM中，並將所有非malloc的記憶體使用分配給快速的DTCM，除非你添加額外的關鍵字來覆蓋優化的預設值。沒有在緊密耦合匯流排上存取的記憶體會優化成DMA存取裝置。由於M7的大部分記憶體存取是在這兩條緊密耦合匯流排上完成的，因此強大的DMA設備能夠高效地存取非TCM記憶體以實現高效的I/O。

Teensy 4.1的Cortex-M7處理器包括一個浮點單元(FPU)，支援64位元的「double」和32位元的「float」。在Teensy 3.5和3.6上的M4 FPU，以及Atmel SAMD51晶片上，只有32位元的float獲得硬體加速。使用double和double函數如log()、sin()、cos()，意味著緩慢的軟體實現數學運算。Teensy 4.1使用FPU硬體執行所有這些運算。

Teensy 4.1 Development board with supercar-level performance

The Teensy 4.1 is the newest iteration of the astoundingly popular development platform that features an ARM Cortex-M7 processor at 600MHz, with a NXP iMXRT1062 chip, four times larger flash memory than the 4.0, and two new locations to optionally add more memory. The Teensy 4.1 is the same size and shape as the Teensy 3.6 (2.4in by 0.7in), and provides greater I/O capability, including 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. On M4, loops and other code which much branch take three clock cycles. With M7, after a loop has executed a few times, the branch prediction removes that overhead, allowing the branch instruction to run in only a single clock cycle.

Tightly Coupled Memory is a special feature which 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) which supports both 64 bit “double” and 32 bit “float”. With M4’s FPU on Teensy 3.5 & 3.6, and also Atmel SAMD51 chips, 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.

Note: Please be aware that the Teensy 4.1 does not include headers and will need to be purchased separately and soldered on yourself.