nrf51822学习笔记之PPI.docx

Programmable Peripheral Interconnect (PPI)功能：PPI 可以实现不同的外设之间通过tasks和events进行自主互动，而不需要用到CPU。The Programmable Peripheral Interconnect (PPI) enables different peripherals to interact autonomously with each other using tasks and events and without having to use the CPU.一个外设的event可以触发另外一个外设的task。The PPI provides a mechanism to automatically trigger a task in one peripheral as a result of an event occurring in another peripheral.PPI通道的作用是使一个event链接 着一个task,每个PPI通道由两个端点寄存器（end-point registers）组成：event端（EEP）和task端（TEP）。A task is connected to an event through a PPI channel. The PPI channel is composed of two end-point registers, the Event End-Point (EEP) and the Task End-Point (TEP).一个外设的task 是通过该task的任务寄存器地址（the address of the task register）与TEP相连的。同理event。当应用程序存在实时要求（real-time constraints exist），又不需要CPU参与时，PPI可以实现外设之间的精确同步。NRF_PPI-CHEN = (PPI_CHEN_CH0_Enabled PPI_CHEN_CH0_Pos) | (PPI_CHEN_CH1_Enabled PPI_CHEN_CH1_Pos);说明：PPI共有16个通道 Channel CH 0:15硬件定义好的通道：3+5+4=12个专用的Channel4个 Group （单个Group使能、Channel使能、置位、清位、TE端设置）015共16个Channel通道#define NRF_PPI (NRF_PPI_Type *) NRF_PPI_BASE)#define NRF_PPI_BASE 0x4001F000UL/* * brief PPI controller. (PPI) */typedef struct / PPI Structure PPI_TASKS_CHG_Type TASKS_CHG4; /Channel group tasks. _I uint32_t RESERVED0312; _IO uint32_t CHEN; / Channel enable. _IO uint32_t CHENSET; /Channel enable set. _IO uint32_t CHENCLR; /Channel enable clear. _I uint32_t RESERVED1; PPI_CH_Type CH16; / PPI Channel. _I uint32_t RESERVED2156; _IO uint32_t CHG4; / Channel group configuration. NRF_PPI_Type;static void ppi_init(void)/* Configure PPI channel 0 to toggle PWM_OUTPUT_PIN on every Timer 2 COMPARE0 match. */ NRF_PPI-CH0.EEP = (uint32_t)&NRF_TIMER2-EVENTS_COMPARE0;NRF_PPI-CH0.TEP = (uint32_t)&NRF_GPIOTE-TASKS_OUT0;/* Configure PPI channel 1 to toggle PWM_OUTPUT_PIN on every Timer 2 COMPARE1 match. */ NRF_PPI-CH1.EEP = (uint32_t)&NRF_TIMER2-EVENTS_COMPARE1; NRF_PPI-CH1.TEP = (uint32_t)&NRF_GPIOTE-TASKS_OUT0;/* Enable only PPI channels 0 an