Going back to electronic after a 20 years break

The blackmagic will show itself as 2 ttyACM devices They can have different names depending on what is connected to the system To solve that, following the blackmagic wiki, the simplest is to create a file in /etc/udev/rules.d/10-blackmagic.rules containing                                           SUBSYSTEM=="tty", ATTRS{interface}=="Black Magic GDB Server", SYMLINK+="ttyBmpGdb" SUBSYSTEM=="tty", ATTRS{interface}=="Black Magic UART Port",SYMLINK+="ttyBmpTarg"   Reboot or use udevadm trigger  , replug the blackmagic and you should see two  devices  /dev/ttyBmpGdb and /dev/ttyBmpTarg These names will stay the same Next, let's write two simple shell scripts to make our life easier : blackmagic.sh: This will flash the file given as argument #!/bin/sh export PORT=ttyBmpGdb ${PREFIX}arm-none-eabi-gdb -ex "target extended-remote /dev/$PORT" -ex "monitor swdp_scan" -ex "attach 1"

Let's build a nice bluepill based blackmagic debugger. why is it worth it ? because it makes it possible to debug a stm32 sw using your usual gdb / gdb frontend VERY easily Shopping list * Bluepill from ebay * 3S1P battery connector + wire Firmware First you need to flash the board with "bluepill" blackmagic firmware. It does not compile out of the box, there is a bad merge with a variable renamed from "speed" to "baudrate". The simpler is to get binaries from this post on the stm32duino forum. There are 2 files in the zip : * blackmagic. bin : main executable, address = 0x8002000 * blackmagic_dfu.bin : Boot loader, address  = 0x8000000 You can flash them using a stl-linkv2 clone from ebay on linux using st-flash write blackmagic_dfu.bin 0x8000000 st-flash write blackmagic.bin 0x8002000 Verifying it works fine : If you plug it through USB, you should see 2 serial interfaces, ttyACM0 and ttyACM1 and an openmoko device

That one made me scratch my head for some time. It happens when we use a voltage difference scheme All of a sudden, the ouput raises while the difference is zero or negative i.e. with all resistors = 1k When v1=0, and v1 > v2, Vout is raising instead of being zero WTF ? It boils down to two lines in the LM358p datasheet : * "Output  Source : 40 mA" * "Output Sink : 50 uA with low output" What does it mean ? If the OpAmp outputs current, like a simple non inverting amplifier, it will max out at 40 mA. So with a 1k Resistor, 40V. Not a problem But, in the case of a difference amplifier, it might want to lower the voltage compared to the "-" pin In that case, also with a 1k Resistor, it can lower by 50 uA*1k = 50 mV maximum ! It means that if the "-" pin is higher than 50mv compared to the + pin, it will pull the output up Example: -Pin=3v +pin=0v Output should be zero, it is ~ 3v. How to fix it ? Simple