SPI_flex Class Reference

A software Master SPI (Serial Peripheral Interface) class that can be instantiated on any mbed LPC1768 general IO pins (p5...p30). More...

#include <SPI_flex.h>

Detailed Description

A software Master SPI (Serial Peripheral Interface) class that can be instantiated on any mbed LPC1768 general IO pins (p5...p30).

Primarily optimized for driving daisy-chained serial display hardware, it provides flexibility beyond on-board SPI hardware capabilities and some automation at the expense of speed. Currently runs full clock speed at about 395kHz. Comment-out code lines testing/setting the automatic chip select for higher speed performance if the chip select feature is not required.

• flexible bit-lengths from 0 .. 4,294,967,295. Not possible with mbed hardware.
• automation of the chip select line which enables all external chips to be loaded with information before latching data in.
• selectable clock polarity and edge trigger (Mode 0 through Mode 3).
• selectable chip select polarity (active-low or active-high).
• latching data in while clock is still active on last bit, **such as required by the Maxim MAX6952. This is not possible with the mbed API, onboard SPI or SSP hardware.
• allows one-shot loading of all daisy-chained hardware registers before latching. Prevents display ghosting effect.

The MAX6952 chip requires the following sequence:

[[http://datasheets.maxim-ic.com/en/ds/MAX6952.pdf]]

1. Take CLK low.
2. Take CS low. This enables the internal 16-bit shift register.
3. Clock 16 bits of data into DIN, D15 first to D0 last, observing the setup and hold times. Bit D15 is low, indicating a write command.
4. Take CS high **(while CLK is still high after clocking in the last data bit).
5. Take CLK low.

Example:

 // Send a byte to a SPI slave, and record the response

 // Chip select is automatic

 #include "mbed.h"
 #include "SPI_flex.h"

 SPI device(p5, p6, p7, p8); // mosi, miso, sclk, cs

 int main() {
     device.frequency(300000);      //to slow clock speed if necessary
     int response = device.writebyte(0xFF);
 }

Definition at line 65 of file SPI_flex.h.

Constructor & Destructor Documentation

Member Function Documentation

    Mode | POL | PHA
    -----|-----|----
      0  |  0  | 0
      1  |  0  | 1
      2  |  1  | 0
      3  |  1  | 1