FPSC Gamma Feature Set Introduction

The footprint of the FPSC Gamma Feature Set module is optimized for size and price and guarantees a particularly high production yield thanks to its highly stable solder joints. FPSC modules have a special pinout divided into three zones: core functionalities are in the center, and special or future processor features can be routed on pins around the outside. With FPSC, you gain flexibility for the future. The pin-compatible modules of a feature set enable product variants and upgrades across processor boundaries - without loss of functionality. To achieve this, pin compatibility and to be able to use all PHYTEC modules, the complete feature set footprint must be provided on your baseboard.

This guide is intended to assist in the design of an FPSC Gamma Feature Set module when creating the schematic and layout of the carrier board. Recommendations are given to strategically prepare your design for other compatible FPSC modules. This design-in guide can be used as a companion document to help understand our carrier board, which is intended to serve as a reference design for customer carrier board designs. There are several factors that need to be considered before designing a carrier board:

• Carrier board schematic
• SoM/Carrier board hardware manual
• Design-In Guide - FPSC Gamma Feature Set (LAN-123e.A5)
• Soldering Guide - FPSC-Based Products Fused Tin Grid Array (FTGA) Information (LAN-128e.A4)

All of these guides/manuals can be found on the following product pages:

• phyFLEX-i.MX 8M Plus FPSC
• phyFLEX-i.MX 95 FPSC
• phyFLEX-AM62Lx FPSC
• phyFLEX-STM32MP25x/MP23x FPSC
• phyFLEX-AM62Px FPSC (COMING SOON)
• phyFLEX-i.MX 91/93 FPSC 

FPSC Gamma Feature Set Advantages

• Solder joint geometry ensures maximum ruggedness and force distribution
• Vibration and shock tests according to the EN 60068-2 series of standards confirm robustness
• FTGA soldering technology compensates for coplanar deviations between the module and baseboard
• Bilateral solder reservoirs minimize the risk of faulty solder joints

FPSC Gamma Feature Set Module Universal Footprint

• FPSC is based on feature sets.
• Processors within a feature set are pin-compatible and interchangeable.
• In the core area of the module are the guaranteed features - common features such as Ethernet, USB, PCIe, GPIO, and more.

Signal Definition

FPSC Feature Set Subclasses

In order to ensure that as many guaranteed features as possible are compatible with each other, the FPSC standard has defined a large number of guaranteed mandatory signals. In addition, we have found that while most processors provide these mandatory signals, some groups of processors stand out with specialized capabilities.  Based on these capability differences, the FPSC standard divides these mandatory signals into subclasses. These sub-classifications make it easier to identify the right group of FPSC SOMS for specific use cases such as vision, HMI, or industrial networking. Below is a brief overview of the current subclasses for our FPSC modules.

Subclass 1 - Vision

Guaranteed Feature - Mipi-CSI

The Vision Subclass is for any application that requires one or more cameras. Some applications include camera-based automation, quality assessment, medical technology, and industrial measurement devices.

Subclass 2 - HMI

Guaranteed Feature - LVDS

The HMI Subclass specializes in using high-quality displays. Uses include smart home automation, automated ticket kiosks, and commercial appliances.

Subclass 3 - Industrial Network

Guaranteed Features - CAN(FD), RGMII

The Industrial Network subclass can be used for any application that requires multiple Ethernet ports or broadcasting sensors. Industrial automation, medical devices, robotics, and avionics applications can all take advantage of this subclass.

FPSC Featureset Signal Types 

3 Feature Types

FPSC Gamma Featureset modules have a concentric pinout with different zones: Core functionalities are mostly located in the center, while optional or future processor features can be routed to pins around the outside.

1. Mandatory Signals
   All modules in a feature set are supported and provide the necessary interfaces to develop many products.
2. Optional Signals
   The Preferred Signals pins are routed to pins currently supported by many processors and should be considered for future System on Modules of the FPSC featureset.
3. Specialized Signals
   The third type allows the use of processor features that are not subject to standardization and are therefore unique to a processor. This allows the use of special and new processor features.

Mechanical Layer

Module

According to the FPSC specification, no fixed PCB sizes and no fixed aspect ratio for a module are defined for Feature Set FPSC-Gamma. To achieve pin compatibility and to be able to use all PHYTEC modules, the complete feature set footprint must be provided on your baseboard.

Baseboard

Footprints/Soldermask

Anchor Joints

In addition to the functional signal pins, solder connections in the form of anchor joints are required to connect the assembly, which includes the baseboard and SoM. These anchor joints do not perform any electrical function; they serve only to mechanically stabilize the connection. They are designed to evenly distribute the forces acting on the circuit boards and relieve the signal pins. Further details on soldering can be found in Soldering Guide - FPSC-Based Products Fused Tin Grid Array (FTGA) Information (LAN-128e.A4) - Solder Paste Optimization

Pin Numbering

Thermal Management/Drill Holes

Surface enlargements (i.e., heatspreaders) are individual for each module. FPSC defines the contact surfaces and the fastening of surface enlargement utilizing the metalized holes (Baseboard - Top View). The holes on the baseboard may be omitted (e.g., device-specific heat dissipation concept, fixing to a SOM). PHYTEC surface enlargements use the holes defined above.

Electrical Layer

Operating Ground/GND

Operating ground pins/GND are marked black in the picture. In addition to the retaining pads, there are the following pins:

Electrical Characteristics

Recommended Operation Conditions

Switching Characteristics

Power Sequencing

All PHYTEC modules have an internal power management system (PMIC) that controls the individual processor voltages and control signals. Complex processors can go into unpredictable states if their power sequencing is incorrect. It is therefore imperative that the specified power sequencing is not affected.

Power-up

All PHYTEC modules start power-up sequencing automatically after the supply voltage is applied. To simplify the design-in, the power-up in PHYTEC modules is optimized for three control lines:

• nPWRREADY_OUT (Pin U22)
• nRESET_OUT (Pin R22)
• nRESET_IN (Pin Y21)

nPWRREADY_OUT is an open-drain output on the module and requires an external pull-up resistor (<12V). nPWRREADY_OUT is pulled to GND by the SOM when all processor voltages are properly brought up. Once nPWRREADY_OUT is pulled to GND, voltages can be applied to the processor pins (e.g., push-pull outputs and pull-up/pull-down resistors). Use nPWRREADY_OUT to control the power to the peripherals connected to the module on your custom baseboard.

nRESET_OUT is an open-drain output on the module with an internal pull-up resistor (1.8 V). nRESET is held to GND during power sequencing. After nPWRREADY_OUT is also pulled to GND, nRESET_OUT may be held to GND for several microseconds. All baseboard peripheral voltages must have ramped up during this time. If it takes more time for these voltages to ramp up, nRESET_IN can be held at GND on the baseboard for as long as necessary. Once nRESET_OUT is switched to high impedance, the processor will begin the boot process. You should connect nRESET_OUT to the reset inputs of your baseboard peripherals. nRESET_OUT is not intended to perform a CPU reset! Use nRESET_IN (Pin Y21) instead (see below).

nRESET_IN is an open-drain input on the module with an internal pull-up resistor (1.8 V to VCC_IN). nRESET_IN is intended to perform a CPU reset. On a falling edge and depending on the module, the module will cycle some or all module power rails to reset the module properly. In this case, nPWRREADY_OUT may switch to a High-Z state as described above. nRESET_IN can be used to delay the boot process by holding it on GND during power-up. After Power-up and on the rising edge, the processor will begin the boot process.

When designing power sequencing for your baseboard, consider the case of a brief loss of external power. You may be using peripherals that operate with a power-on reset. To ensure that these peripherals are always in a defined state, an additional discharge of the voltages switched via nPWRREADY_OUT is often a useful addition.

Power-cycle/Reset

nRESET_IN (pin Y21) is an open-drain input with an internal pull-up resistor. Use nRESET_IN to trigger a reset or power-cycle the module. You can connect nRESET_IN to a push-button or open-drain output.

On the falling edge of nRESET_IN, the module starts the reset sequence. nPRWREADY (U22) may be set to HIGH-Z during that.

On the rising edge of nREST_IN, the processor will begin the boot process, and nRESET_OUT will be set to a High-Z state.

IO Voltage

FPSC defines an IO voltage of 1.8 V for all interfaces to enable optimum system integration. However, in consultation with our sales team, you have the option of using an IO voltage of 3.3 V for specific interfaces if this meets your requirements. Please note that this option is limited by the individual characteristics of the processor used and therefore requires prior technical testing.

SOM-Features

In addition to physical compatibility (e.g., pinout, signal level, geometry), other software-level functions are also considered. These functions (SOM features) are available on every SOM. They are an integral part of the FPSC Gamma feature set and enable the reusability of baseboard designs and software components across different SOM variants.

The following features are mandatory for all SOMs:

• Primary Debug-UART
  Standardized serial interface for outputting boot messages and communicating with the bootloader or kernel console on UART3.

• Special Debug-UART
  Debug interface, e.g., for integrated co-processors on UART2.

• RTC (Real-Time Clock)
  Each SOM has an integrated RTC and allows, among other things, the system time to be maintained when the system is switched off.

• EEPROM
  An EEPROM for storing SOM-specific information, e.g., for the bootloader and customer-specific project data, is always available.

• Mass Storage (e.g., eMMC or NAND)
  Each SOM has integrated, non-volatile mass storage. The specific technology (e.g., eMMC or NAND) depends on the SOM, while the storage size and speed are variable via configuration options.

• Ethernet-PHY
  An Ethernet PHY is fully integrated into the SOM. To implement an Ethernet interface on the baseboard, all that is needed is a transformer (magnetics) and a suitable socket (typically an RJ-45).

Boot Source Selection

FPSC Gamma Feature Set provides 4 signals for boot source selection. The signals BOOT_MODE0 (Pin P25), BOOT_MODE1 (Pin R24), BOOT_MODE2 (Pin T25), and BOOT_MODE3 (Pin U24) are usually connected directly to the processor. The boot mode is evaluated by the processor in relation to the rising nRESET edge. If the signals for boot source selection on the baseboard are not connected (open), an internal mass storage device is set as the default boot source for the user-stage bootloader.

Possible boot sources for the user-stage bootloader could be:

• (SOM) internal NOR-Flash
• (SOM) internal eMMC
• (SOM) internal Bootfuses (referring to another boot source)
• SD-Card
• Ethernet
• USB-Serial
• USB-Mass Storage
• UART

If an interface is available more than once, at least the first interface can always be used as the boot source. The user-stage bootloader may provide additional options for loading the operating system (e.g., kernel and file system).

Interfaces

All signals refer to 1.8V IO voltage unless otherwise noted.

If an interface exists more than once, they are numbered starting from 1. The ordering is determined by

1. Bootability, boot source first.
2. The maximum achievable data rate of the interface, starting with the fastest.

SD-Card Interface

The modules provide the power supply for the SD card. The interface allows various “bus speed modes” that the SD card can negotiate with the host processor. The logic voltage may be 3.3 V or 1.8 V, depending on the SD card used. No additional circuitry is required on the baseboard (except capacitors for VCC) as the module implements the logic for this. The CD and WP signals have an internal pull-up.

SDIO4 Interface

The modules have a preferred SDIO interface. This SDIO interface is 4 bits wide and can also contain the nWP and CD control signals. In addition, the IO reference voltage of the interface is brought out at pin J56.

CAN(-FD) Interface

You can always rely on a CAN interface. If a processor supports CAN-FD, it can be used on the baseboard with an appropriate transceiver. Due to its backward compatibility, CAN-FD can also be used in a CAN system.

UART

There are 3 UART interfaces with different prioritization.

• Primary Debug Interface for debug outputs of the main CPU
• Special Debug Interface for debug outputs of the support CPU (if available)
• A normal UART interface with no special function for the baseboard

All UARTs work as DTE (TxD and RTS are outputs, RxD and CTS are inputs). Under certain circumstances, the signal direction can be reversed within the CPU. You can find more information on this in the processor data sheet.

USB

USB1 is by default the interface to support USB OTG (Host- and Device), in case the processor supports USB OTG. If the Processor does not support OTG, USB1 will be in Host Mode.

Pinout

The signal direction is defined from the module's point of view.

PWR/CTRL

GPIO/PWM

SAI

QSPI

ADC

SD Card/SDIO4

CAN/I2C/I3C/SPI/UART

PCIE

LVDS

HDMI

DSI

CSI

Ethernet

RGMII

USB

GND

Specialized Pins

Specialized pins are reserved for interfaces that are unique to a particular processor or System on Module (SoM) and are not standardized within the FPSC pinout. These pins are routed to module pins so that all processor features can be accessed and utilized without restrictions, regardless of whether they are part of the standardized FPSC pinout. Using these signals makes cross-module compatibility very unlikely and cannot be guaranteed for these pins. However, using specialized pins alongside FPSC-compliant pins does not affect their compatibility. Some of these pins may be reserved for future use in case new, unforeseen interfaces are introduced through a minor revision of the FPSC standard. For more information about these interfaces and signals, please refer to the hardware manual specific to your SoM. These manuals detail signal names, types, voltage domains, and recommended configurations.

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