Solis-(25-40)K-4G inverter DSP firmware updating procedure

Most current DSP firmware version: 38 for 25K, 30K, 36K, and 40K --- 3B for 36K fanless and 40K fanless

For the following inverter models:


Solis-25K-US-SW, Solis-30K-US-SW, Solis-36K-US-SW, Solis-40K-US-SW, Solis-40K-US-F-SW, Solis-25K-US, Solis-30K-US, Solis-36K-US, Solis-40K-US, Solis-40K-US-F 

Note: A Solis Update Stick is required in order to perform DSP and HMI firmware updates. Please reach out to your distributor or to Solis US Service to obtain an Update Stick. 

Solis inverters have two kinds of firmware: Digital Signal Processor (DSP) and Human-Machine-Interface (HMI)


25-40K Procedure 

  1. Verify Firmware Version: Advanced Info > PWD 0-0-1-0 > Version 

25-40K Display – DSP Version is 07 shown below        


  1. Prepare the Files for the USB Stick: 

  1. There are two files that should be on the USB stick. 

  1. If the service engineer provides a full file name for example DSP-480-HV-V31.bin rename the file to “28335APP.bin”. 

  1. If the service engineer provides a file that is named 28335APP.bin then do not rename it. 

  1. Add the 28335API.bin file and the 28335APP.bin file to the USB Directory. 

  1. Ensure no other files or folders are in the USB directory. 


    1. Prepare the Inverter and Install Firmware 

    1. Go to Advanced Setting – Password 0010 - Grid On/Off and turn the Grid to Off. 

    1. Insert the USB Stick in the bottom of the firmware update tool 

    1. Insert the 6-pin cable into the firmware update tool.  

    1. If you have a USB battery bank or other power source, connect it to the endoscope that is taped along the length of the wooden dowel.  This will power a small LED light that will help you see inside the inverter upper cabinet: 

    1. The DSP board has an RJ-45 port this used to upgrade the DSP firmware.  The RJ-45 connector on the other end of the 6-pin cable needs to be inserted into this port for the firmware upgrade to be applied. 

    In the picture below, the DSP board is located inside the inverter upper cabinet in the location marked by the blue rectangle.  The red arrow shows the path the cable will take to reach the board. 


    1. To access the DSP board with the update tool/cable, unscrew the plastic knockout at the top right side of the inverter 

    1. Next, slowly insert the RJ-45 end of the wooden dowel into the DSP access knockout, looking down the “barrel” to identify the RJ-45 port on the DSP board (there is only one of them). 

    1. Insert the RJ-45 connector into the port on the DSP board. 

    1. The RJ-45 connector has been taped to the wooden dowel such that the edge of the dowel will help push the RJ-45 connector into the port.  

    1. The retaining clip on the RJ-45 connector has been removed, so that it can be easily removed when the update is complete. 

    1. When the Firmware Update Tool is successfully connected to the RJ-45 Port, you should see the Red and Green lights on the update tool to come on. 

    1. Next, hold down the reset button on the tool until the Red and Orange Lights are lit: 

    1. Next, Click the reset button and wait until the lights stop flashing. 

    1. If the orange light goes out (dark) and only the red light is lit, then the firmware update failed.  Check all connections and re-attempt the upgrade. 

    1. If the red light and either the green OR orange light light up (depending on inverter model), the update is complete. 

    1. Disconnect cable from the DSP board, replace the plastic knockout, and check the software version again to confirm that the DSP upgrade was successful (if Software Version is no longer displayed in the Version screen, hold the UP and DOWN buttons together for 3 seconds, until Software Version appears. 

    1. When the DSP update is confirmed, turn the inverter back on and verify operation. 

Victor is the author of this solution article.

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