This is an old revision of the document!
Table of Contents
SPI group
This group defines all used Serial Peripheral Interface (SPI) interfaces.
Each SPI interface is a sub group with the SPI name as the group name.
"SPI": {
"encoder_spi": {
"pad_sck": "PA5",
"pad_miso": "PA6",
"pad_mosi": "PA7",
"pad_ncs": "PA15",
"peripheral" : "SPI0",
"role": "master",
"communication_mode": "duplex",
"frame_format": "motorola",
"clock_polarity": "idle_low",
"clock_phase": "sample_on_leading_edge",
"bit_order": "msb_first",
"baud_rate": "10 MHz",
}
}
pad_sck
Serial Clock.
type: String
pad_mosi
“Master Out Slave In” data signal.
type: String
pad_miso
“Master In Slave Out” data signal.
type: String
pad_ncs
Chip Select signal (Low active).
type: String
peripheral
name of the SPI peripheral to use.
type: String
role
Is either master(host) or slave(device).
type: enum
default: master
communication_mode
Describes the communication. Possible values are:
- duplex : the traditional mode using MISO and MOSI to transmit and receive at the same time.
- half-duplex : meaning the same wire between master and slave is used for both directions.
- receive-only : send line is not used
- send-only : receive Line is not used.
type: enum
default: duplex
frame_format
Describes the communication. Possible values are:
- motorola : the “normal” SPI.
- ti :
type: enum
default: motorola
clock_polarity
Also often called CPOL. Describes the communication. Possible values are:
- idle_low
- idle_high
type: enum
default: idle_low
clock_phase
Also often called CPHA. Describes the communication. Possible values are:
- sample_on_leading_edge : samples the data on the edge from idle value to non-idle value.
- sample_on_trailinging_edge : samples the data on the edge from non-idle value to idle value.
type: enum
default: sample_on_leading_edge
SPI Mode
Sometimes the documentation talks about a SPI Mode with the value of 0 to 3. This mode maps to the phase and polarity as described in the following table:
| Mode | CPOL | CPHA | description |
|---|---|---|---|
| 0 | 0 | 0 | clock: idle_low, phase: sample_on_leading_edge |
| 1 | 0 | 1 | clock: idle_low, phase: sample_on_trailing_edge |
| 2 | 1 | 0 | clock: idle_high, phase: sample_on_leading_edge |
| 3 | 1 | 1 | clock: idle_high, phase: sample_on_trailing_edge |
bit_order
Describes the communication. Possible values are:
- msb_first : most significant bit first (bits on the line : 76543210 )
- lsb_first : least significant bit first (bits on the line: 01234567 )
type: enum
default: msb_first
baud_rate
Is the number of bits per second exchanged on the data lines. Expressed as frequency of the clock line.
type: int (Hz)