I bought the DSO 138 Kit which is a 20$ oscilloscope. It is very good if you are a DIY electronics enthusiast who doesn’t have 200-300$ for a proper oscilloscope or 60-100 $ for a pc oscilloscope or small portable oscilloscope. It is a kit so you have to solder the smd and through hole component to the PCB. The instructions are pretty good, I assemble the kit in 4 hours and it worked on the the first try. But 1 week later the left trace of the oscilloscope went up and the signal appeared to be negative. To fix this i had to update the firmware. Follow the Steps below:
Step 1. Go here and download the New firmware under the
Step 2. Download STSW-MCU005 from here.
Step 3. Sort out the JP1 and JP2 connection in the back of the PCB
Step 4. Get a USB to Serial converter like FTDI FT232RL wich has 5 and 3.3 volt RX TX lines (put the jumber on the 3.3 volt). Connect the RX pin from the FT232RL to the TX pin of the DSO 138, the TX pin to the RX and GND to GND. Power Up the DSO 138
Srep 5. Install the Flash Loader which is in the stsw-mcu005.zip file you downloaded before (In my PC when i installed the Flash Loader there wasn’t any sort cat in the Desktop to open the program, if you have the same problem just go to C:\Program Files (x86)\STMicroelectronics\Software\Flash Loader Demo and create a sort cat for STMFlashLoader Demo). When you open the Flash Loader go to the port name and select the COM port in which the FT232RL is connected then press next, again next, select Download to Device and Brows the hex file you downloaded in step 1.
Step 6. Enjoy
By Dimitris Xarir.