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Texas Instruments TPS6598x PDIO Alternate Mode Application notes
Application Report
SLVA855 – February 2017
TPS6598x PDIO Alternate Mode
ABSTRACT
The PDIO Alternate Mode allows users to transmit or receive up to four unique digital signals between two
systems connected through USB Type-C. The PDIO signals are particularly applicable to applications
such as laptop docking stations, where push button events can be used to send status information from
one device to another like a virtual GPIO. This application report explains the standard implementation of
the PDIO Alternate Mode and is to be used with Texas Instruments TPS6598x family of USB Type-C and
USB PD controllers and associated software tools.
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Contents
Introduction ................................................................................................................... 2
PDIO Configuration in Host Interface Registers ......................................................................... 2
PDIO Example ............................................................................................................... 3
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Block Diagram................................................................................................................ 2
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Texas Instruments VID Config Panel ..................................................................................... 2
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GPIO Config Panel .......................................................................................................... 3
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PDIO Settings ................................................................................................................ 4
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GPIO Settings ................................................................................................................ 4
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PD Messages
List of Figures
................................................................................................................
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Introduction
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Introduction
PDIO is a feature of TI alternate mode which allows to transmit or receive up to four slow digital signals
between two systems which are connected using USB Type-C connections.
TPS6598x
Type-C
TPS6598x
GPIOs
GPIOs
The TPS6598x USB Type-C and USB PD controllers can be configured to transmit or receive up to four
digital signals to another compatible controller connected using USB Type-C connections. The user can
use any four GPIOs in PDIO mode. Any change in these GPIOs is automatically transmitted over the USB
Type-C link to the compatible receiver connected on the other side.
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Figure 1. Block Diagram
The PDIO feature is useful for applications such as laptop docking stations, where these GPIOs can be
used to send push button events and control LEDs to indicate various states of the system.
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PDIO Configuration in Host Interface Registers
The TPS65982 registers include the following:
• Configuration registers
– 0x54, Texas Instruments VID Config Register
– 0x5C GPIO Event Map Register
The Texas Instruments VID Config Register (0x5C) is the primary register used to control PDIO mode in
the TPS6598x PD controllers. This register allows the user to enable Texas Instruments VID, PDIO Mode
and auto entry. This register also allows the user to set the message index and PDIO signature.
Figure 2. Texas Instruments VID Config Panel
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TPS6598x PDIO Alternate Mode
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PDIO Example
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The Message Index field is used to assign an array location in the billboard failure message if it occurs.
According to the current setting shown in Figure 2, the seventh item in the array sent by the billboard
device contains information about PDIO.
The PDIO Signature field is a 32-bit field to assign a unique signature to a set of devices that are
supposed to work together. For the PDIO feature to work, both the ends connected to the Type-C cable
must have an identical PDIO signature. The last 4 bytes of the PDIO must be 0x0451 whereas the first 4
bytes can be assigned by the user. Therefore the format of the PDIO is 0xABCD0451, where ABCD is a
user-assigned number.
The GPIO Event Map Register (0x5C) is used to configure the GPIOs of the TPS6598x devices. Using
this register the user can assign any supported feature to a GPIO including a PDIO-input or PDIO-output
function.
Figure 3. GPIO Config Panel
Each TPS6598x device can have a maximum of 4 PDIOs which can be configured either as an input or
output.
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PDIO Example
The TPS6598x Application Customization Tool contains multiple project templates, most of which can
support a PDIO data transfer.
Create a new project in TPS6598x Application Customization Tool and go to the Texas Instruments VID
Config option in the Shared Device Settings tab as shown in Figure 4.
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PDIO Example
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Figure 4. PDIO Settings
Enter the settings into the tool exactly as shown in Figure 4. Ensure that the PDIO Signature field has
identical values for both the connected USB Type-C and USB PD controllers.
Go to the GPIO Event Map option and select up to 4 GPIOs as either input or output as shown in
Figure 5. Set the other applicable settings appropriately and program the PD controllers.
Figure 5. GPIO Settings
Connect both ends using a USB Type-C cable and ensure that the VBUS supply goes to the correct value
depending on the configuration of the controllers.
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PDIO Example
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Toggle one or more PDIO inputs and observe the change in state of the corresponding PDIO outputs on
the other end.
The resulting scope of Type-C communication during PDIO changes should be similar to Figure 6.
Figure 6. PD Messages
Figure 6 shows the expected sequence of PD operations for this example. The change of GPIO is
communicated as an Alternate Mode message.
• Initially, the system makes an initial contract and alternate mode communication to negotiate the
contract.
• Whenever the PDIO input GPIO changes in one direction, that direction sends out an Alternate Mode
message to send out this information.
• The other end receives this information and accordingly changes the state of the mapped GPIO.
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