Overview

SPI 為資料傳輸協定，有著以下幾點特色：

.. benfit is what?

• 同步式
• 全雙工
  • 可以半雙工或單工
• 主從式
  • dynamic change of master/ slave
  • 多個 master
• 8 master baud rate prescalers
• slave mode frequency
• SPI TI / motorola mode
• MSB-first or LSB-first
• Hardware CRC
• DMA capability .. BIDI mode / RXONLY (p. 801) .. I2S feature

Device overview

.. image:: /embedded/SPI/STM32F40x block diagram.png STM32F40x block diagram [#]_

.. [#] DS8626: ARM Cortex-M4 32b MCU+FPU, 210DMIPS, up to 1MB Flash/192+4KB RAM, USB OTG HS/FS, Ethernet, 17 TIMs, 3 ADCs, 15 comm. interfaces & camera <http://www.st.com/internet/com/TECHNICAL_RESOURCES/TECHNICAL_LITERATURE/DATASHEET/DM00037051.pdf>_ p.18

• 3 SPI
  • SPI1: 37.5 Mbits/s
  • SPI2 & SPI3: 21 Mbits/s

.. Datasheet: p.32

SPI functional description

general

.. 介紹 pin

.. image:: /embedded/SPI/SPI block diagram.png SPI block diagram [#]_

.. [#] STM32F405xx, STM32F407xx , STM32F415xx and ... <http://www.st.com/internet/com/TECHNICAL_RESOURCES/TECHNICAL_LITERATURE/REFERENCE_MANUAL/DM00031020.pdf>_ p.793

• MISO: Master In / Slave Out data
• MISO: Master Out / Slave In data
• SCK: Serial Clock ( Master -> Slave )
• NSS: (optional) select slave, low-driven

.. image:: /embedded/SPI/single master _ single slave application.png SPI single master/single slave application [#]_

.. [#] STM32F405xx, STM32F407xx , STM32F415xx and ... <http://www.st.com/internet/com/TECHNICAL_RESOURCES/TECHNICAL_LITERATURE/REFERENCE_MANUAL/DM00031020.pdf>_ p.794

.. baud rate ref menual p.834

.. Slave select(NSS) pin management ’’’’’’’’’’’’’’’’’’’’’’’’’’’’’’’’

Clock phase and clock polarity ’’’’’’’’’’’’’’’’’’’’’’’’’’’’’’

.. image:: /embedded/SPI/SPI Dota clock timing diagram.png Data clock timing diagram[#]_

.. [#] STM32F405xx, STM32F407xx , STM32F415xx and ... <http://www.st.com/internet/com/TECHNICAL_RESOURCES/TECHNICAL_LITERATURE/REFERENCE_MANUAL/DM00031020.pdf>_ p.796

SPI_PR1 中有兩個 bits CPOL 和 CPHA 控制取值的時間關係，

• CPOL(clock polarity) 決定閒置時 clock 的電位，CPOL = 0 表閒置時為低電位。
• CPHA(clock phase) 決定在 clock 的哪個 edge 取值， CPHA = 0 表示在第一個 edge (到不同電位時)取值。

Data format ’’’’’’’’’’’

• LSB-first or MSB first
• 一次傳送的資料量為 8-bit 或 16-bit

confiurataion in master mode

confiurataion in slave mode

half-duplex communication

• BIDMODE 判斷是否為全雙工
• RXONLY 判斷半雙工時為傳送端或接收端。

SPI 可以只做半雙工，在半雙工時，沒用到的另一隻 pin 可作為一般的 GPIO 使用。

.. RXONLY 在 BIDMODE 時有作用否？

data transmission and reception procedures

CRC calculation

Status flag

Disabling SPI

Code section

Reference

• Serial Peripheral Interface Bus - Wikipedia, the free encyclopedia <http://en.wikipedia.org/wiki/Serial_Peripheral_Interface_Bus>_
• Reference manual: STM32F405xx, STM32F407xx , STM32F415xx and ... <http://www.st.com/internet/com/TECHNICAL_RESOURCES/TECHNICAL_LITERATURE/REFERENCE_MANUAL/DM00031020.pdf>_
• Datasheet: DS8626: ARM Cortex-M4 32b MCU+FPU, 210DMIPS, up to 1MB Flash/192+4KB RAM, USB OTG HS/FS, Ethernet, 17 TIMs, 3 ADCs, 15 comm. interfaces & camera <http://www.st.com/internet/com/TECHNICAL_RESOURCES/TECHNICAL_LITERATURE/DATASHEET/DM00037051.pdf>_

.. need improve

.. _Reference manual: http://www.st.com/internet/com/TECHNICAL_RESOURCES/TECHNICAL_LITERATURE/REFERENCE_MANUAL/DM00031020.pdf