Polling

This sample application note describes using SPI3W polling mode to read sensor ID.

Communicates with the sensor via SPI3W and reads the specified information by reading the data under the specified address.

Requirements

The sample supports the following development kits:

Development Kits
Hardware Platforms	Board Name
RTL87x2G HDK	RTL87x2G EVB

For more requirements, please refer to Quick Start.

Wiring

EVB external PWM3610DM-SUDU sensor, connect P2_2 and CLK, P2_3 and SDIO, P2_4 and CS#, and also connect GND and VDD.

Hardware Introduction

The PWM3610DM-SUDU is a laser sensor module. The PMW3610DM-SUDU registers are accessible through the serial port. The registers are used to read motion data and status, as well as to set the device configuration. In this example, it is used to demonstrate communication with SPI3W.

Building and Downloading

This sample can be found in the SDK folder:

Keil

Project file: samples\peripheral\spi3wire\polling\proj\rtl87x2g\mdk

GCC

Project file: samples\peripheral\spi3wire\polling\proj\rtl87x2g\gcc

To build and run the sample, follow the steps listed below:

Open sample project file.
To build the target, follow the steps listed on the Generating App Image in Quick Start.
After a successful compilation, the app bin app_MP_xxx.bin will be generated in the directory mdk\bin or gcc\bin.
To download app bin into EVB board, follow the steps listed on the MP Tool Download in Quick Start.
Press reset button on EVB board and it will start running.

Experimental Verification

When the EVB starts, it prints the ID information. If the ID is 0x3e and 0x01 (only for PWM3610DM-SUDU sensor), it means the test is successful.
```
id[0] = 0x3e, id[1] = 0x01
SPI3W test pass!
```

Code Overview

This chapter will be introduced according to the following several parts:

Source Code Directory.
Peripheral initialization will be introduced in chapter Initialization.
Functional implementation after initialization will be introduced in chapter Functional Implementation.

Source Code Directory

Project Directory: sdk\samples\peripheral\spi3wire\polling\proj
Source Code Directory: sdk\samples\peripheral\spi3wire\polling\src

Source files are currently categorized into several groups as below.

└── Project: polling
    └── secure_only_app
        └── Device                   includes startup code
            ├── startup_rtl.c
            └── system_rtl.c
        ├── CMSIS                    includes CMSIS header files
        ├── CMSE Library             Non-secure callable lib
        ├── Lib                      includes all binary symbol files that user application is built on
            └── rtl87x2g_io.lib
        ├── Peripheral               includes all peripheral drivers and module code used by the application
            ├── rtl_rcc.c
            ├── rtl_pinmux.c
            └── rtl_spi3w.c
        └── APP                      includes the ble_peripheral user application implementation
            ├── main_ns.c
            └── io_spi3w.c

Initialization

The initialization process includes board_3wire_spi_init and driver_3wire_spi_init .

board_spi3w_init contains the PAD and PINMUX settings.

Config PAD: Set pins as PINMUX mode, PowerOn, internal Pull-None.
Configure PINMUX: Set pin P2_2 to the SPI2W_CLK function, pin P2_3 to the SPI2W_DATA function, and pin P2_4 to the SPI2W_CS function.

driver_spi3w_init contains the initialization of spi3wire peripheral.

Enable PCC clock.
Set the system clock and the SPI3W output clock.
Set the working mode to SPI_3WIRE_MODE.
Set the delay time for reading data.
Set the output to generate no delay.
Set SPI3W to normal mode.

RCC_PeriphClockCmd(APBPeriph_SPI3W, APBPeriph_SPI3W_CLOCK, ENABLE);
...
SPI3W_InitStruct.SPI3W_SysClock       = 20000000;
SPI3W_InitStruct.SPI3W_Speed          = 800000;
SPI3W_InitStruct.SPI3W_Mode           = SPI3W_3WIRE_MODE;
SPI3W_InitStruct.SPI3W_ReadDelay      = 0x3;
SPI3W_InitStruct.SPI3W_OutputDelay    = SPI3W_OE_DELAY_NONE;
SPI3W_InitStruct.SPI3W_ExtMode        = SPI3W_NORMAL_MODE;

Functional Implementation

The resync signal of SPI3W. Set the duration of the resync signal, enable the resync signal output, and wait for the resync signal output to complete before disabling the resync signal.

SPI3W_SetResyncTime(2);
SPI3W_ResyncSignalCmd(ENABLE);
while (SPI3W_GetFlagStatus(SPI3W_FLAG_RESYNC_BUSY) == SET);
SPI3W_ResyncSignalCmd(DISABLE);

Execute SPI3W_Cmd() to enable SPI3W.
Execute spi3wire_readbyte to read the sensor ID.
1. Wait for the SPI3W_FLAG_BUSY flag bit to clear.
2. Clear the data in the receive FIFO of SPI3W.
3. Read one of the data from the sensor through SPI3W and wait for the busy status flag bit to clear.
4. Read the data in the receive FIFO of SPI3W.
5. Return the read data and print.

/* Check spi busy or not */
while (SPI3W_GetFlagStatus(SPI3W_FLAG_BUSY) == SET)
...

SPI3W_ClearRxDataLen();
SPI3W_StartRead(address, 1);

while (SPI3W_GetFlagStatus(SPI3W_FLAG_BUSY) == SET)
...

while (SPI3W_GetRxDataLen() == 0);
SPI3W_ReadBuf(&reg_value, 1);

return reg_value;