Configuring SPI

QNX SDP8.0SPI Framework TechnotesAPIConfiguration

This chapter describes how to configure the SPI configuration file, spi.conf. The chapter includes rules for editing the file sections and their parameters.

Configuring the spi.conf file

QNX SDP8.0SPI Framework TechnotesAPIConfiguration

You can edit the SPI configuration file, spi.conf, to match the SPI bus and devices layout of your target. The default file path is /etc/system/config/spi/spi.conf. You can use this file (or one similar) by specifying the file path as the parameter to the SPI driver -c command line option.

The file contains specific configuration sections. Each section describes the parameters which can be set. Each section starts with a [<section type>] declaration. All parameters after the [<section type>] declaration belong to the declared section, up to the next [<section type>] declaration (or end-of-file). The [] character sequence should not appear in any non-commented section elsewhere in the file.

For the purpose of documentation, this file includes all parameters along with their default values, but commented out with '#'. When editing, retain the known default value by copying the line and changing the value. All comments follow a '#' until the end-of-line. White space is ignored unless otherwise stated.

Rules for the config file

The following rules must be followed when editing spi.conf:
  1. Only alphanumeric characters are allowed for section name.
  2. Only alphanumeric characters and '_' are allowed for parameter name.
  3. Must have at least one bus section in each config file.
  4. Must have at least one dev section under each bus.
  5. In each bus section, all the mandatory parameters must be set.
  6. In each bus section, bus number and bus name cannot duplicate.
  7. In each dev section, all the mandatory parameters must be set.
  8. Under the same parent bus, dev number and dev name cannot duplicate.
  9. In each dev section, the parent_busno has to be an existing busno in previous bus sections.

Configuration sections

The spi.conf file has the following sections:
Section Description
globals Specifies a SPI global configuration.
bus Specifies a SPI bus configuration.
dev Specifies a SPI device configuration.

Configure globals section

QNX SDP8.0SPI Framework TechnotesAPIConfiguration

The globals section specifies the configuration to apply globally to SPI.

Parameters:

The following parameters are configurable under the globals section:

Parameter Description Type Possible values (if applicable)
verbose SPI driver and io-spi debuggers print verbosity. The -v command-line option of the spi-XXX driver overrides the verbose value in the config file. Integer

Example:

The following code block is an example of a globals section: 
[globals]
verbose=5

Configure bus section

QNX SDP8.0SPI Framework TechnotesAPIConfiguration

The bus section specifies the configuration to apply to a SPI bus.

Parameters:

The following parameters are configurable under the bus section:
Parameter Description Mandatory Type Possible values (if applicable)
busno Bus number Yes Integer
name Bus name Yes String See Configuring the spi.conf file.
base Bus base address Yes Hexadecimal 0x00000000 - 0xFFFFFFFF.
irq Bus IRQ (interrupt request) number. Yes Integer
input_clock bus input clock Yes Integer Unit Hz
bs Board or controller specific parameters No String Default NULL
dma_init_opts DMA initialization options No String Default NULL.
dma_attach_opts DMA attach options No String Default NULL.
dma_thld DMA threshold No Integer Default 0.

Example:

The following code block is an example of a bus section: 
[bus]
busno=0
name=spi0
base=0xfe204000
irq=150
input_clock=500000000
bs=rpanic=48,tpanic=16
dma_attach_opts=num_cbs=256,range_min=0,range_max=14,typed_mem=sysram&below1G

Configure dev section

QNX SDP8.0SPI Framework TechnotesAPIConfiguration

The dev section specifies the configuration to apply to a device connected to the same SPI bus.

Note:
The dev section has to be after its parent bus section and has to provide its parent_busno. Otherwise, the dev section won't be added to device list.

Parameters:

The following parameters are configurable under the dev section:
Parameter Description Mandatory Type Possible values (if applicable)
parent_busno Parent bus number of the device Yes Integer
devno Device number Yes Integer
name Device name Yes String See Configuring the spi.conf file.
clock_rate Bus speed for the device Yes Integer Unit Hz
cpha SPI CPHA No Integer Options are: 0 or 1. Default 0.
cpol SPI CPOL No Integer Options are: 0 or 1. Default 0.
bit_order SPI bit order No String Options are: MSB or LSB. Default MSB. Case insensitive.
word_width SPI transfer word width in bits No Integer Options are: 8, 16, or 32. Default 8.
idle_insert SPI idle insertion support No Integer Options are: 0 or 1. Default 0.

Example:

The following code block is an example of a dev section: 
[dev]
parent_busno=0
devno=0
name=dev0
clock_rate=5000000
cpha=1
word_width=32

Example of spi.conf

QNX SDP8.0SPI Framework TechnotesAPIConfiguration
The following spi.conf example has one globals section and two bus sections, spi0 and spi3. Bus spi0 has two dev sections, while spi3 has one dev section. Notice how each of the dev sections come after its parent bus section, indicated by the parent_busno of each dev sections. 
#############################  S E C T I O N  ##################################
# Section globals
[globals]
verbose=5
#############################  S E C T I O N  ##################################
# Section bus
[bus]
busno=0
name=spi0
base=0xfe204000
irq=150
input_clock=500000000
bs=rpanic=48,tpanic=16
dma_attach_opts=num_cbs=256,range_min=0,range_max=14,typed_mem=sysram&below1G
#############################  S E C T I O N  ##################################
# Section dev
[dev]
parent_busno=0
devno=0
name=dev0
clock_rate=5000000
cpha=1
#############################  S E C T I O N  ##################################
# Section dev
[dev]
parent_busno=0
devno=1
name=dev1
clock_rate=5000000
cpol=1
#############################  S E C T I O N  ##################################
# Section bus
[bus]
busno=3
name=spi3
base=0xfe204600
irq=151
input_clock=500000000
#############################  S E C T I O N  ##################################
# Section dev
[dev]
parent_busno=3
devno=0
name=dev0
clock_rate=5000000
word_width=32
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