martijnbastiaan/cocotbext-spi

Protocol test extension for testing spi in cocotb

cocotbext-spi

Protocol test extension for testing spi in cocotb

install

To use this module the easyiest way is to

• clone the repository :

$ git clone https://github.com/Martoni/cocotbext-spi.git

• Then install it with pip (tested with python 3.7):

$ python -m pip install -e cocotbext-spi/

With this method if cocotbext-spi code is modified, modification will be taken into account in your testbench directly. Without having to re-install module.

How to use it

Simply include the module in your testbench :

from cocotbext.spi import *

cocotbext-spi module include Master side test. The module SPIModule() is seen as a SPI master and dut SPI interface as a slave.

Master

cocotbext-spi is composed of two classes :

• SPIConfig(): to describe configuration
• SPIModule(): the test module inherit from Driver and Monitor.

And one Tuple for signals :

• SPISignals : used to give dut signals names.

Three steps should be done in initialization of your testbench (often in __init__() function of your testbench).

1. Define dut pinout, filling the tuple :

spi_sigs = SPISignals(miso=dut.miso,
                      mosi=dut.mosi,
                      sclk=dut.sclk,
                      cs=dut.csn)

2. Set configuration with class SPIConfig:

self.spi_config = SPIConfig(cpol=False,
                            cpha=True,
                            baudrate=(1, "us"),
                            csphase=False)

3. Then instantiate the SPIModule:

self.clock = cocotb.Clock(dut.clock, 10, units="ns")
self.spimod = SPIModule(self.spi_config, spi_sigs, self.clock)

In your reset procedure/function, init SPI signals with method sig_init() without yield.

Once the bench started, a monitor will read permanently the two signals mosi and miso and register values read.

Mosi is written with method send(byte) 8 bits by 8 bits. And chip select signal must be toggled manually with set_cs(True/False). For example to do a 16bits data write with 7 bits addr + 1 bit R/W like for Spi2Wb components we will do :

self.spimod.set_cs(True) # enable chip select
yield sclk_per
yield self.spimod.send(0x80|addr) # send 8 bits data 
yield self.spimod.send((value >> 8)&0x00FF) # value is 16bits then we
yield self.spimod.send(value&0x00FF)        # send it in two steps
yield sclk_per
self.spimod.set_cs(False) # disable chip select

For reading, we have to wait for monitor to receive values with :

ret = yield self.spimod.wait_for_recv(1) # waiting for receive value

The return value is a dict of bitstring with mosi and miso value read in the chip select interval :

values_recv = {"miso": miso, "mosi": mosi}

A usage example can be seen for testbench part of project Spi2Wb.

Slave

To be implemented