microbit 硬體架構介紹

2017-04-04 18:14

Microbit 硬體架構介紹

文章來至http://tech.microbit.org/hardware/

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這篇內容為近期整理介紹,我們盡可能維持正確性,若有發現錯誤,請參考 GitHub here上的資料為佐證參考

概述

·        Overview 概述

·        Getting Started With the micro:bit Hardware 如何開始使用microbit

·        Hardware Description 硬體構造及零件說明

o   nRF51 Application Processor 藍芽主要IC

o   Bluetooth Wireless Communication 藍芽通訊描述

o   Low Level Radio Communications  無線通訊描述(同樣用2.4Ghz , 但不是用藍芽通訊協定)

o   Buttons 按鍵

o   Display 顯示屏

o   Accelerometer 重力感測器

o   Magnetometer 磁力感測器

o   Temperature Sensing 溫度感測

o   General Purpose Input/Output Pins 數位輸入出

o   Power Supply 電力供應

o   Interface 介面IC 說明

o   USB Communications USB 通訊

o   Debugging  除錯

o   Mechanical  機構

·        Links 相關連結

 

如何開始使用microbit 硬體

Microbit 硬體設計是根據ARM mbed技術所開發的應用IC及相干周邊功能所設計出來的! 另外有一顆介面IC 用來處理USB 介面及拖拉式核心軟體更新法.這介面IC 並未用來連結任何周邊.

兩部分關鍵資訊可以一窺Microbit 的內部設計:

·        線路圖(schematics), 可以看到主要零件的連結方式及設計.

·        參考設計及相關模組資料(reference design), 這部分的資料可以幫助進一步了解Microbit 的設計及變動性

.

 

硬體相關說明

nRF51 應用處理器IC

 nRF51 應用處理器IC是讓使用者作主要程式控制的處理器,完整的程式包含了使用者客制及中介層(runtime) 及藍芽協議層(Stack),(譯者註:瀏覽器編譯環境會在使用者程式寫完同時,將這三部分整合完成) 一旦使用者將完整程式(HEX 檔)放在USB 快閃記憶體根目錄上,處理器便會直接執行程式碼。使用者也可對連接在這處理器上的GPIO去做控制. 也可透過 2.4GHz 無線去做相關周邊的控制.

項目

說明

Model

Nordic nRF51822-QFAA-R rev 3

Core variant

ARM Cortex-M0 32 bit processor

Flash ROM

256KB

RAM

16KB

Speed

16MHz

Debug

SWD, jlink/OB

More Info

here

 

 

 

 

 

藍芽通訊

板子上2.4G無線相關設計提供了對手機平板的藍芽通訊功能

項目

說明

Stack

Bluetooth 4.1 with Bluetooth low energy

Band

2.4GHz ISM (Industrial, Scientific and Medical) 2.4GHz..2.41GHz

Channels

50 2MHz channels, only 40 used (0 to 39), 3 advertising channels (37,38,39)

Sensitivity

-93dBm in Bluetooth low energy mode

Tx Power

-20dBM to 4dBm in 4 dB steps

Role

GAP Peripheral

Congestion avoidance

Adaptive Frequency Hopping

Profiles

BBC micro:bit profile

More Info

here

 

 

 

無線通訊

板子上2.4G無線相關設計提供另外的無線通訊協議(Nordic Gazell),這通訊協議已經在不同的程式語言環境可以直接使用,並且可以在多個microbit 裝置中互相傳遞並且群組化(group code ).

項目

說明

Protocol

Nordic Gazell

Freq band

2.4GHz

Channel rate

1Mbps or 2Mbps

Encryption

None

Channels

101 (0..100)

Group codes

255

Tx power

Eight user configurable settings from 0(-30dbm) to 7 (+4dbm)

Payload size

32 (standard) 255 (if reconfigured)

More Info

here

 

 

 

按鍵

Microbit 正面有兩個按鈕,背面有一個。背面的按鍵連接至KL26 介面IC及 nRF51 處理器做系統重制用(reset)

正面的按鍵A 、 B 是可以由使用者去做程式控制包括了短壓、長壓或是A、B同時按,按鍵A、B 均連接至金手指(edge connector)上的GPIO ,加上電路設計可以做logic 0 或 1值的操作.

項目

說明

Type

2 tactile user buttons, 1 tactile system button

Debounce

(A & B) software debounced, 54ms period

Pullup

(A & B) external 4K7, (System) 10K

 

 

 

顯示

在板子上有5x5 陣列LEDs.做為顯示屏,microbit  是以3x9 陣列電路去控制它.並用很高的速度去刷新它。以下暫不翻譯但保留( LED matrix is also used to sense ambient light, by repeatedly switching some of the LED drive pins into inputs and sampling the voltage decay time, which is roughly proportional to ambient light levels.)

項目

說明

Type

minature surface mount red LED

Physical structure

5x5 matrix

Electrical structure

3x9

Intensity control

10 steps

Intensity range

TBC

Sensing

ambient light estimation via software algorithm

Sensing Range

TBC, 10 levels from off to full on

Colour sensitivity

red centric, red is 700nm

 

 

 

重力感測器(加速度感測器)

重力感測器是經由I2C 跟處理器連結,並提供了三軸的感應資料並包含了手勢感測的演算法 (like : fall detection, logo-up, logo-down, shake)

項目

說明

Model

Freescale MMA8653FC

Features

3 axis, 2/4/8g ranges

Resolution

10 bits (0..1023)

Max output data rate

800Hz

On board gestures

‘freefall’

Other gestures

Other gestures are implemented by software algorithms in the runtime.

 

 

 

磁力感測器

磁力感測器也是透過I2C 跟處理器連結,提供了磁力感測數值,並提供指南針功能, (The compass must be calibrated before use, and the calibration process is automatically initiated by the runtime software – 譯者對這段有些疑慮,暫不翻譯)

項目

說明

Model

Freescale MAG3110

Max update rate

80Hz

Full Scale range

1000uT

Sensitivity

0.10uT

 

 

 

溫度感測

nRF51 處理器提供了板子上的即時溫度感測(Run time ambient temperature sensing ).

項目

說明

Type

on-core nRF51

Sensing range

-25C .. 75C

Resolution

0.25C steps

Accuracy

+/-4C (uncalibrated)

More Info

here

 

 

 

數位輸入輸出(GPIO)

金手指 (edge connector) 上有許多 GPIO 。處理器上有許多的多工訊號針腳(pin define) ,有些已經設定成GPIO 功能連接至金手指,如何進一步使用這些針腳請參閱 (nRF51 data sheet)

項目

說明

Rings

3 large IO rings and two large power rings, 4mm plug and crocodile clip compatible

GPIO features

19 assignable GPIO pins

 

2 are assigned to the on board I2C interface

 

6 are used for display or light sensing feature

 

2 are used for on board button detection

 

1 is reserved for an accessibility interface

 

19 may be assigned as digital input or digital output

 

19 may be assigned for up to 3 simultaneous PWM channels

 

19 may be assigned for 1 serial transmit and 1 serial receive channel

 

6 may be assigned as analog input pins

 

3 may be assigned to an optional SPI communications interface

 

3 may be assigned for up to 3 simultaneous touch sensing inputs

ADC resolution

10 bit (0..1023)

Edge Connector

Edge connector data sheet

Pitch

1.27mm, 80 way double sided.

Pads

5 pads, with 4mm holes

More Info

here

 

 

 

電力供應

給microbit的電力,主要是由介面IC透過USB 提供,亦可由電池盒連接器提供,在金手指上亦有電力供應的功能,需要熟悉電路設計的人操作.

項目

說明

Operating range

1.8V .. 3.6V

USB current

120mA max

Onboard Peripherals budget

30mA

Battery connector

JST X2B-PH-SM4-TB

Battery current

TBC

Max current provided via edge connector

90mA

More Info

here

 

 

 

介面

這介面IC提供USB連結功能、拖拉式程式刷新(drag and drop flash program)及跟主電腦做序列通訊(serial communication) .

項目

說明

Model

Freescale MKL26Z128VFM4

Core variant:

ARM Cortex-M0+

Flash ROM

32KB

RAM

4KB

Speed

16MHz

Debug capabilities

SWD

More Info

here

 

 

 

USB通訊

主要意思跟上一段雷同,不做翻譯但保留原文(The micro:bit has an on board USB communications stack, that is built into the firmware of the interface chip. This stack provides the ability to drag and drop files onto the MICROBIT drive in order to load code into the application processor. It also allows serial data to be streamed to and from the micro:bit application processor over USB to an external host computer, and supports the CMSIS-DAP protocol for host debugging of application programs.)

項目

說明

Connector

USB micro, MOLEX_47346-0001

USB version

1.1 Full Speed device

Speed

12Mbit/sec

USB classes supported

Mass Storage Class (MSC)

 

Communications Device Class (CDC)

More Info

here

 

 

 

除錯

譯者尚未做過這段的實務操作所以暫不翻譯先保留原文(The interface processor can be used with special host tools to debug code that is running on the application processor. It connects to the application processor via 4 signal wires. The KL26 interface processor code can also be debuged via it’s integral SWD software debug interface, for example to load initial bootloader code into this processor at manufacturing time, or to recover a lost bootloader.)

項目

說明

Protocol

CMSIS-DAP

Options

JLink/OB (via different firmware)

More Info

here

 

 

 

機構

我們有提供2D 跟3D CAD 圖檔,這些資料可以用來提供microbit 行銷及專案資料甚至3D printing 的生產製造的圖檔資料.

項目

說明

Dimensions

5cm(w) 4cm(h)

Weight

5g

 

 

Micro:bit 中文台湾 中國

相關連結

Schematic

Reference Design

Nordic NRF51 datasheet

Freescale KL26 reference manual

Freescale KL26Z data sheet

Freescale MMA8652 accelerometer datasheet

Freescale MAG3110 magnetometer datasheet

Technical Specifications 1

Technical Specifications 2

Safety Advice

I2C specification

SPI ‘specification’

ARM mbed overview

 

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