[][src]Crate imxrt1062_fcb_gen

This crate is unmaintained. Consider using imxrt-boot-gen, which provides a similar API and works across iMXRT processor variants.

A library for generating an iMXRT106X Firmware Configuration Block (FCB) from Rust. Intended to be used in build.rs build scripts to generate FCBs for iMXRT106x-based systems.


The iMXRT106x Firmware Configuration Block (FCB) is an array that describes how the processor should initiate a boot. It's expected to be placed in a certain region of FLASH, with values that describe how a peripheral should interact with NAND- / NOR-based FLASH memory. The FCB has a lot of magic numbers, and it would be nice to have an API to generate the FCB.

The imxrt1062-fcb-gen crate provides an API for generating the FCB. As of this writing, it supports only the generation of an FCB for reading NOR Flash via FlexSPI. Other configurations, such as NAND Flash and / or the SEMC interface, may be added later.


Add imxrt1062-fcb-gen to your build dependencies:

imxrt1062-fcb-gen = { path = "../imxrt1062-fcb-gen" }

Then, instantiate a Builder in your build.rs build script. Unless a member of the Builder implements Default, it's probably required and it requires your input. See the iMXRT1062 reference manual for details that may be missing from this library.

Once the builder is built, write the FCB instance from your build script, and include it using the include! macro in your crate. See the teensy4-fcb crate for an example.


The output is a single u8 array, called FIRMWARE_CONFIGURATION_BLOCK. The name is not mangled. It may be referenced in a linker script by its section, ".fcb".


The example below demonstrates how we might define the FCB for a Teensy 4.

use imxrt1062_fcb_gen::*;

// We're using serial NOR flash.
let nor_cb = nor::ConfigurationBlock {
    page_size: nor::PageSize::new(256),
    sector_size: nor::SectorSize::new(4096),
    ip_cmd_serial_clk_freq: nor::SerialClockFrequency::MHz30,
// Load the lookup table with our magic numbers. Numbers
// that are not specifed are set to `0`.
let lookup_table = {
    let mut lookup = LookupTable::new();
    lookup.insert_u32(0, 0x0A18_04EB);
    lookup.insert_u32(1, 0x2604_3206);
    lookup.insert_u32(4, 0x2404_0405);
    lookup.insert_u32(12, 0x0000_0406);
    lookup.insert_u32(20, 0x0818_0420);
    lookup.insert_u32(32, 0x0818_04D8);
    lookup.insert_u32(36, 0x0818_0402);
    lookup.insert_u32(37, 0x0000_2004);
    lookup.insert_u32(44, 0x0000_0460);
// Define the FCB
let builder = Builder {
    read_sample_clock_source: ReadSampleClockSource::LoopbackFromDQSPad,
    cs_hold_time: CSHoldTime::new(0x01),
    cs_setup_time: CSSetupTime::new(0x02),
    column_address_width: ColumnAddressWidth::other_devices(),
    device_mode_configuration: DeviceModeConfiguration::Disabled,
    wait_time_cfg_commands: WaitTimeConfigurationCommands::disable(),
    device_mode_seq: DeviceModeSequence::new(0, 0),
    flash_a1_size: SerialFlashSize::new(0x0020_0000),
    flash_a2_size: SerialFlashSize::default(),
    flash_b1_size: SerialFlashSize::default(),
    flash_b2_size: SerialFlashSize::default(),
    serial_clk_freq: SerialClockFrequency::MHz60,
    serial_flash_pad_type: FlashPadType::Quad,
    device_type: DeviceType::SerialNOR(nor_cb),
// Build the FCB
let fcb = builder.build().unwrap();
// Write it to a string. It could also be written to
// a file, or to an `std::io::Writer`.
let fcb_string = format!("{}", fcb);

// The string will resemble something like the following...
// #[link_section = ".fcb"]
// #[no_mangle]
// pub static FIRMWARE_CONFIGURATION_BLOCK: [u8; 512] = [
//     0x46, // 0x000 Tag 'FCFB'
//     0x43, // 0x001
//     0x46, // 0x002
//     0x42, // 0x003
//     0x00, // 0x004 Version 'bugfix'
//     0x00, // 0x005 Version 'minor'
//     0x01, // 0x006 Version 'major
//     0x56, // 0x007 Version 'V'
//     0x00, // 0x008 RESERVED
//     0x00, // 0x009 RESERVED
//     0x00, // 0x00A RESERVED
//     0x00, // 0x00B RESERVED
//     0x01, // 0x00C readSampleClkSrc
//     0x01, // 0x00D csHoldTime
//     0x02, // 0x00E csSetupTime
//     0x00, // 0x00F columnAddressWidth
//     0x00, // 0x010 deviceModeCfgEnable
//     0x00, // 0x011 RESERVED
//     0x00, // 0x012
//     0x00, // 0x013 waitTimeCfgCommands
//     0x00, // 0x014 deviceModeSeq
//     // Rest elided for clarity...
// ];



Fields specific for NOR flash



Type tag for SerialFlashSize


Type tag for SerialFlashSize


Type tag for SerialFlashSize


Type tag for SerialFlashSize


Builder for a firmware configuration block definition


Serial flash CS hold time


Serial flash CS setup time


Column address width


deviceModeArg, only useful when paired with DeviceModeConfiguration.


Sequence parameter for device mode configuration


The firmware configuration block


The lookup table, part of the general FCB memory region.


sFlashXXSize field, where XX is one of A1, A2, B1, B2.


Wait time for all configuration commands



Describes both the deviceModeCfgEnable field, and the deviceModeArg field, which is only valid if the configuration is enabled.


Describes the deviceType field.


sFlashPad field


readSampleClkSrc of the general FCB