Electronics- Serial Communication-SPIdenethor.wlu.ca/pc320/lectures/spibeam.pdf · 2018-10-03 ·...

transcript

Serial Communication -SPIRaspberry Pi Python SPI Library

ElectronicsSerial Communication-SPI

Terry Sturtevant

Wilfrid Laurier University

October 3, 2018

Terry Sturtevant Electronics Serial Communication-SPI

Serial Communication -SPI

Serial Peripheral InterfaceMaster/slave communicationUses 3 signals (and Ground),MISO, MOSI, SCLKand chip selects for each slave deviceSynchronous, so master controls clock rate

Serial Peripheral Interface

Master/slave communicationUses 3 signals (and Ground),MISO, MOSI, SCLKand chip selects for each slave deviceSynchronous, so master controls clock rate

Serial Peripheral InterfaceMaster/slave communication

Uses 3 signals (and Ground),MISO, MOSI, SCLKand chip selects for each slave deviceSynchronous, so master controls clock rate

Serial Peripheral InterfaceMaster/slave communicationUses 3 signals (and Ground),MISO, MOSI, SCLKand chip selects for each slave device

Synchronous, so master controls clock rate

Serial Peripheral InterfaceMaster/slave communicationUses 3 signals (and Ground),MISO, MOSI, SCLKand chip selects for each slave deviceSynchronous, so master controls clock rate

0 1 2 3 4 5 6 76 6 6 6 6 6 6 6

SPI transfers can happen in both directions simultaneously.

0 1 2 3 4 5 6 76 6 6 6 6 6 6 6

SPI transfers can happen in both directions simultaneously.

PySpidev

spi = spidev.SpiDev()create objectspi.open(0,0)open port, deviceThere is normally one SPI port on the Raspberry Pi.It is designated as port 0SPI0 has two associated devices, selected by chip selectsCE0 and CE1So, spi.open(0,0) means toconnect to the device using CE0 on SPI0

PySpidev

spi = spidev.SpiDev()create object

spi.open(0,0)open port, deviceThere is normally one SPI port on the Raspberry Pi.It is designated as port 0SPI0 has two associated devices, selected by chip selectsCE0 and CE1So, spi.open(0,0) means toconnect to the device using CE0 on SPI0

PySpidev

spi = spidev.SpiDev()create objectspi.open(0,0)open port, device

There is normally one SPI port on the Raspberry Pi.It is designated as port 0SPI0 has two associated devices, selected by chip selectsCE0 and CE1So, spi.open(0,0) means toconnect to the device using CE0 on SPI0

PySpidev

spi = spidev.SpiDev()create objectspi.open(0,0)open port, deviceThere is normally one SPI port on the Raspberry Pi.

It is designated as port 0SPI0 has two associated devices, selected by chip selectsCE0 and CE1So, spi.open(0,0) means toconnect to the device using CE0 on SPI0

PySpidev

spi = spidev.SpiDev()create objectspi.open(0,0)open port, deviceThere is normally one SPI port on the Raspberry Pi.It is designated as port 0

SPI0 has two associated devices, selected by chip selectsCE0 and CE1So, spi.open(0,0) means toconnect to the device using CE0 on SPI0

PySpidev

spi = spidev.SpiDev()create objectspi.open(0,0)open port, deviceThere is normally one SPI port on the Raspberry Pi.It is designated as port 0SPI0 has two associated devices, selected by chip selectsCE0 and CE1

So, spi.open(0,0) means toconnect to the device using CE0 on SPI0

PySpidev

spi = spidev.SpiDev()create objectspi.open(0,0)open port, deviceThere is normally one SPI port on the Raspberry Pi.It is designated as port 0SPI0 has two associated devices, selected by chip selectsCE0 and CE1So, spi.open(0,0) means toconnect to the device using CE0 on SPI0

PySpidev

(continued)

So, spi.max speed hz = 5000 means tolimit the SPI clock speed to about 5kHzresponse = spi.xfer2([0xAA])transfer one byteCS held active between blocksresponse = spi.xfer([values])transfer bytesCS realeased and reactivated between blocks

PySpidev

(continued)So, spi.max speed hz = 5000 means tolimit the SPI clock speed to about 5kHz

response = spi.xfer2([0xAA])transfer one byteCS held active between blocksresponse = spi.xfer([values])transfer bytesCS realeased and reactivated between blocks

PySpidev

(continued)So, spi.max speed hz = 5000 means tolimit the SPI clock speed to about 5kHzresponse = spi.xfer2([0xAA])transfer one byteCS held active between blocks

response = spi.xfer([values])transfer bytesCS realeased and reactivated between blocks

PySpidev

(continued)So, spi.max speed hz = 5000 means tolimit the SPI clock speed to about 5kHzresponse = spi.xfer2([0xAA])transfer one byteCS held active between blocksresponse = spi.xfer([values])transfer bytesCS realeased and reactivated between blocks

PySpidev (continued)

spi.writebytes([values])write bytesspi.readbytes(len)read len bytesspi.cshighget or set active state of CSspi.close()close port

spi.writebytes([values])write bytes

spi.readbytes(len)read len bytesspi.cshighget or set active state of CSspi.close()close port

spi.writebytes([values])write bytesspi.readbytes(len)read len bytes

spi.cshighget or set active state of CSspi.close()close port

spi.writebytes([values])write bytesspi.readbytes(len)read len bytesspi.cshighget or set active state of CS

spi.close()close port

spi.writebytes([values])write bytesspi.readbytes(len)read len bytesspi.cshighget or set active state of CSspi.close()close port

PySpidev sample code

impor t s p i d e vs p i = s p i d e v . SpiDev ( )s p i . open (0 , 0 ) #port , d e v i c e

# use po r t 0 , ch i p s e l e c t CE0s p i . max speed hz = 5000w h i l e True :

s t r v a l = i n p u t (” v a l ( 0 . . . 2 5 5 , q=q u i t ) : ” )i f s t r v a l == ’q ’ :

b reake l s e :

v a l u e = i n t ( s t r v a l )dummy = s p i . x f e r 2 ( [ 4 9 , v a l u e ] )

s p i . c l o s e ( )

PySpidev sample code

impor t s p i d e vs p i = s p i d e v . SpiDev ( )s p i . open (0 , 0 ) #port , d e v i c e

# use po r t 0 , ch i p s e l e c t CE0s p i . max speed hz = 5000w h i l e True :

s t r v a l = i n p u t (” v a l ( 0 . . . 2 5 5 , q=q u i t ) : ” )i f s t r v a l == ’q ’ :

b reake l s e :

v a l u e = i n t ( s t r v a l )dummy = s p i . x f e r 2 ( [ 4 9 , v a l u e ] )

s p i . c l o s e ( )

Electronics- Serial Communication-SPIdenethor.wlu.ca/pc320/lectures/spibeam.pdf · 2018-10-03 ·...

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