d544e3c2f6
Also update docs to reflect the max label length. Fixes #738. Signed-off-by: Alex Tereschenko <alext.mkrs@gmail.com> Signed-off-by: Brendan Le Foll <brendan.le.foll@intel.com>
128 lines
6.5 KiB
Markdown
128 lines
6.5 KiB
Markdown
JSON platform {#jsonplat}
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=============
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JSON platform loading allows libmraa users who work with **simple** and unsupported
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boards to create JSON configuration files which libmraa understands, allowing
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libmraa to just 'work' with the unsupported platform. JSON platform **does not work**
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with boards which require advanced functions which overwrite default functionality or
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boards that require the mux functionality.
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Syntax
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------
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The JSON file that libmraa reads needs specific values to be set by default, they
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are required in every JSON file intended to be used to load the platform.
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The keywords are case sensitive so be aware when writing the JSON file.
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Each heading is a top level key in the JSON file, each key's type is Array
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### platform
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|Key |Type |Required |Description |
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|-------------|-------|-----------|-----------------------------------------------|
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|id |int |no | An ID that can be assigned |
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|name |string |yes | The platform name |
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|pin_count |int |yes | The total pin count |
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|gpio_count |int |no | The subset of pincount which able to do GPIO |
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|i2c_count |int |no | The number of usable I2C ports |
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|aio_count |int |no | The number of usable AIO ports |
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|spi_count |int |no | The number of usable SPI ports |
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|uart_count |int |no | The total UART ports |
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|pwmDefPeriod |int |no | The default PWM period |
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|pwmMaxPeriod |int |no | The max PWM period |
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|pwmMinPeriod |int |no | The min PWM period |
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### layout
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**THIS INDEX'S THE PIN ARRAY**
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Each available pin specified using pin_count requires a label. There is no need to use an
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index identifier as the json objects are indexed as they are read, starting with the first
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json object being treated as index 0.
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The number of json objects in layout should be equal to the pin_count.
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|Key |Type |Required |Description |
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|-----------|-------|-----------|-----------------------------------------------|
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|label |string |yes | The label used to describe the pin (11 characters max) |
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|invalid |boolean|no | Sets the labeled pin as an invalid pin |
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### GPIO
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**THIS INDEX'S THE PIN ARRAY**
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For the supported GPIO pins here is where we set the raw linux pin it needs to use, the
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index cannot exceed the total pin_count and the number of JSON ojects cannot exceed the
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gpio_count total. The index is also used to set the specified pin's capabilities. Each set
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of keys should be enclosed in a json object.
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|Key |Type |Required |Description |
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|-----------|-------|-----------|-------------------------------------|
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|index |int |yes | used to index the pin array |
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|rawpin |int |yes | used to reference the actual IO pin |
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### I2C
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**THIS INDEX'S THE I2C ARRAY**
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This is used to setup the I2C functionality. The total number of json objects and the index
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cannot exceed the i2c_count. Each set of keys should be enclosed in a json object.
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|Key |Type |Required |Description |
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|-----------|-------|-----------|-------------------------------------|
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|index |int |yes | Used to index the I2C array |
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|rawpin |int |yes | The sysfs pin |
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|sclpin |int |no | The clock pin |
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|sdapin |int |no | The data pin |
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|default |boolean|no | Sets the default I2C device used |
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### AIO
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**THIS INDEX'S THE PIN ARRAY**
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This is used to setup which pins are able to perform AIO. Each set of keys should be
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enclosed in a json object.
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|Key |Type |Required |Description |
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|-----------|-------|-----------|-------------------------------------|
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|index |int |yes | Used to index the pin array |
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|rawpin |int |yes | The sysfs pin |
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### PWM
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**THIS INDEX'S THE PIN ARRAY**
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This is used to setup which IO pins can do PWM Each set of keys should be enclosed in a
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json object.
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|Key |Type |Required |Description |
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|-----------|-------|-----------|-------------------------------|
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|index |int |yes | Used to index the pin array |
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|rawpin |int |yes | The sysfs pin |
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|chipID |int |yes | The parent ID |
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## SPI
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**THIS INDEX'S THE SPI ARRAY**
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This is used to setup the SPI functionality. The total number of json objects and the index
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cannot exceed the spi_count. Each set of keys should be enclosed in a json object.
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|Key |Type |Required |Description |
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|-----------|-------|-----------|--------------------------------------------|
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|index |int |yes | The index into the SPI array |
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|chipID |int |yes | The parent ID |
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|clock |int |no | The clock used for transmissions |
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|miso |int |no | Pin used for incoming data from the slave |
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|mosi |int |no | Pin used for outgoing data from the master |
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|chipselect |int |no | Pin used to select the slave device |
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|default |boolean|no | Sets the default SPI device |
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### UART
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**THIS INDEX'S THE UART ARRAY**
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This is used to setup the UART functionality. The total number of json objects and the index
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cannot exceed the uart_count. Each set of keys should be enclosed in a json object.
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|Key |Type |Required |Description |
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|-----------|-------|-----------|-----------------------------------------|
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|index |int |yes | Used to index the UART array |
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|chipID |int |yes | Parent ID |
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|rawpin |int |yes | Sysfs pin |
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|rx |int |no | Read pin |
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|tx |int |no | Transmit pin |
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|path |string |yes | Used to talk to a connected UART device |
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|default |boolean|no | Sets the default UART device |
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