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BurstSPI Class Reference
An SPI Master, used for communicating with SPI slave devices at very high speeds. More...
|BurstSPI (PinName mosi, PinName miso, PinName sclk)|
|Create a SPI master connected to the specified pins. |
|void||fastWrite (int data)|
|Put data packet in the SPI TX FIFO buffer. |
|Use this function before fastWrite to set the correct settings. |
|After you are done with fastWrite, call this function. |
|void||format (int bits, int mode=0)|
|Configure the data transmission format. |
|void||frequency (int hz=1000000)|
|Set the spi bus clock frequency. |
|virtual int||write (int value)|
|Write to the SPI Slave and return the response. |
An SPI Master, used for communicating with SPI slave devices at very high speeds.
The default mbed SPI class allows for communication via the SPI bus at high clock frequencies, however at these frequencies there is alot of overhead from the mbed code. While this code makes sure your code is alot more robust, it is also relative slow. This library adds to your default SPI commands some extra commands to transmit data rapidly with very little overhead. Downsides are that currently it is TX only (all RX packets are discarded), and it requires some extra commands.
//Send 1000 SPI packets as fast as possible spi.setFormat(); for (int i = 0; i<1000; i++) spi.fastWrite(data[i]); spi.clearRX();
As an example, writing 76,800 16-bit data packets to an LCD screen at 48MHz requires 111ms with the normal mbed library. With this library it takes 25ms, which is also the theoretical amount of time it should take. If you are running at 1MHz this will do alot less.
Constructor & Destructor Documentation
Member Function Documentation
After you are done with fastWrite, call this function.
FastWrite simply fills the SPI's (SSP's actually) TX FIFO buffer as fast as it can, and that is the only thing it does. It doesn't do anything with received packages (currently, may change), so the the RX buffer is full with unneeded packets. This function waits until transmission is finished, and clears the RX buffer. You always have to call this before you want to receive SPI data after using fastWrite.
|void fastWrite||(||int||data )|
Put data packet in the SPI TX FIFO buffer.
If there is no space in the FIFO buffer it will block until there is space. The FIFO buffer will automatically send the packets. There is no receiving here, only transmitting.
data Data to be sent to the SPI slave
|int|| mode =
Configure the data transmission format.
bits Number of bits per SPI frame (4 - 16) mode Clock polarity and phase mode (0 - 3)
mode | POL PHA -----+-------- 0 | 0 0 1 | 0 1 2 | 1 0 3 | 1 1
|void frequency||(||int|| hz =
Set the spi bus clock frequency.
hz SCLK frequency in hz (default = 1MHz)
Use this function before fastWrite to set the correct settings.
It is not needed to use this if the last SPI commands were either normal SPI transmissions, or setting different format/frequency for this object. It is required to call this function when several SPI objects use the same peripheral, and your last transmission was from a different object with different settings. Not sure if you should use it? Use it, it takes very little time to execute, so can't hurt.
|virtual int write||(||int||value )||
Write to the SPI Slave and return the response.
value Data to be sent to the SPI slave
- Response from the SPI slave
Generated on Tue Jan 8 2019 04:27:25 by 1.7.2