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Table of Contents

Embedded module TQMa28 - PTXdist Linux BSP documentation

Known Issues



RS485 bus block in half-duplex mode
Affects RS485 via UARTx
Issue During i.MX28 reset the UARTx.CTS# pin is low by default (CPU internal pull down)
Effect Using the MBa28 RS485 circuitry in a half-duplex slave device or half-duplex multi-master environment may block the RS485 bus during i.MX28 reset.
The bus is released as soon as the UARTx.CTS# pin is properly configured by software (e.g. U-Boot, Linux, etc.)
Solution / Workaround Add a 10k pull up to the UARTx.CTS# signal on carrier board

TQMa28 & TQMa28-fsl | e-MMC drive strength (SETDSR)
  • Affected hardware revisions: TQMa28 module REV0200
  • Impact: eMMC drive strength (card to host) is too high in card default configuration. This degrades signal integrity and has the potential to degrade the lifetime.
  • Solution: use only new linux / u-boot from BSP REV0106 or port the required changes to your bootloader /operating system.
  • Details: Starting with hardware REV0200 a new eMMC type with better performance characteristics is used on TQMa28. This eMMC features a configurable drive strength (MMC CMD4 - SET_DSR, see JEDEC Standard No. 84-A441, Table 22)
    To keep signal integrity and prevent degrading the lifetime of the processor the following configuration step for the eMMC must be implemented:
    • Write 0x0100 + 16 Stuff bits using CMD4 to the card everytime the card is selected using CMD7
  • The current state of the changes needed in BSP REV0106 for:
    • U-Boot 2013.04 (TQMa28/28L): modifies device tree before booting linux to incorporate DSR value for eMMC value
    • U-Boot 2009.08 (TQMa28-fsl): modifies linux command-line to incorporate DSR value for eMMC value
    • Linux 3.10 (TQMa28/28L): value of DSR parsed from device tree property
    • Linux 2.6.35 (TQMa28-fsl): value of DSR parsed from kernel command-line

Both device tree and command-line implement the value as “tq,dsr”.

TQMa28 & TQMa28-fsl | U-Boot | Firmware Updates via SD card
  • Affected Revisions: 0100, 0101
  • Issue: Unable to extract sizes of images on SD card ⇒ Unable to calculate required sectors to save image
  • Workaround: whole uboot/kernel partitions copied
TQMa28 | U-Boot | Environment location
  • Affected Revisions: 0101
  • Issue: Environment gets saved to and loaded from hard-coded mmc device 0
  • Workaround: none - future release: replace hard-code with dynamic code
TQMa28 | U-Boot | VDDA Brownout
  • Affected Revisions: 0101
  • Issue: The brownout value of register HW_POWER_VDDA is set to 100 mV below 1.8 V. During boot voltage drops >100mV occur. For the VDDA_BO being too close the device powers down and thus stops after the Kernel line “TCP established hash table entries”.
  • Workaround: Increase brownout span to 150 mV.
    –> At the U-Boot prompt type: mw 80044050 0x0008260c
    –> You may also automate this by changing default boot command: setenv bootcmd “mw 80044050 0x0008260c; $bootcmd”; saveenv
TQMa28-fsl | Linux | Ethernet Issue
  • Affected Revisions: 0101
  • Issue: Ethernet link cannot be established to 10 mbit half duplex counterpart
  • Workaround: none - fixed in future release
TQMa28 | Linux 3.5 | GPIO0 IRQ
TQMa28 | Linux 3.5 | Login as non-root
  • Affected Revisions: all up to 0103
  • Issue: “adduser X; login X” results in message “Killed”
  • Workaround: This issue will be fixed in BSP 0103.
    Until then set Kernel config option CONFIG_DEFAULT_MMAP_MIN_ADDR to 32768. Find it at Kernel features - Low address space to protect from user allocation
TQMa28 | Linux 3.5 | USB device connected before boot
  • Affected Revisions: BSP 0102
  • Issue: The Operating System does not recognize USB devices if they are plugged in before boot.
  • Workaround: Modify the Devicetree. Add/change at usb@80090000 the following property “dr_mode” to “dr_mode = host”

en/arm/tqma28/linux/ptxdist/known_issues.txt · Last modified: 2019/07/30 14:51 by liedmann


TQ-Systems GmbH provides the Board Support Packages (BSP) free of charge. The software included in the shipment has been configured individually for the starter kits. The software is only intended to evaluate the module. The use of the Board Support Packages (BSP) is only allowed within the scope of functionality described by TQ-Systems GmbH. TQ-Systems GmbH does not accept any liability for all further changes of the Board Support Package and for any damage resulting from its use.

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