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CHR Serial Interface – Configuration broken

Welcome to Redshift Labs Forums UM7 Product Support CHR Serial Interface – Configuration broken

  • This topic has 4 replies, 2 voices, and was last updated 8 years ago by iris.
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  • #617


    we have a UM7 sensor, which has been great so far. But now I have run into an impossible issue.

    For testing purposes I lowered the internal serial speed from 115.200 to 19.200. The sensor keeps on working but the low baud rate has a negative impact on latency (which is pretty much what I expected, but oh well).

    The issue is this: I cannot put it back to the original value, because for that I would have to use CHR Serial Interface v3.1.1 to set the Configuration again.
    The low baud rate of 19.200 however is not sufficient to download the current Configuration from the UM7 before the Timeout sets in and stops the download. Without a valid download of the current Configuration, however, I cannot edit it.

    Is there a way to increase the Timeout to a couple minutes (or even infinity)?

    This is just too silly, I cannot imagine this really being a problem.


    i found a somewhat whacky work around. even if the download fails, it is then possible to check the “Show advanced settings”, which will show data. with some luck, you can then edit, RAM Commit and even FLASH Commit values.


    Hi Velcrome,

    This is a known issue when lowering the baud rate. If the UM7 is trying to put more data on the bus than can fit given the current baud rate, then it ends up dropping packets. If you are doing a configuration register read, then it can time-out because the response packets are being dropped.

    The workaround is to turn off most or all data transmission before lowering the baud rate, and then gradually increasing what is transmitted to ensure that the bus doesn’t get overwhelmed.

    It is also good to avoid issuing a WRITE_TO_FLASH command until it is verified that the new rate is working properly, so that you can cycle the power to revert the settings if there is a problem.

    If you do get stuck with a swamped bus, you can either issue a RESET_TO_FACTORY command to load the original baud rate, or if that doesn’t work, you can reflash the firmware to restore all default settings.

    To reflash the firmware:

    1) download the most recent version of the firmware from here: (it’s under the “resources” tab).
    2) With the UM7 powered off, short the BOOT pin to any 3.3V output pin on the UM7
    3) Power the device. The status LED should remain off if the bootloader starts properly.
    4) In the Serial Interface, select the downloaded firmware. Make sure that the serial port baud rate is 115200. Click “program” WITHOUT clicking “connect” first.
    5) Once programming is complete, remove the BOOT to 3.3V short and cycle the power.


    Dear Caleb: I have done all the steps you mentioned, I know that the bootloader is active because de led is off, but I obtain the following messages in the CH Serial interface: “conecting to Serial Port”, “programming device” and finally “PROGRAMMING FAILED-Device unavailable.Is the bootloader activated?”.

    Could you please help me? 🙁


    In adittion, Im Reading the UM7 with Labview, and I still can do it without problems, the issue is when I try to connect to the CH robotics Serial Interface, I need to change the configuration of the IMU and now I can´t even connect it.. The timeout Error appears.

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