Assembly done — and now?

So you just assembled yourself a tinyFISH FC ? Congratulations, you just completed the hardest part. Uploading all software bits and bytes should be quite easy compared to those 0402 sized components — so first of all relax!

You will need the following tools:

• tinyFISH FC
• Soldering iron
• Lab power supply
• Mbicro USB cable
• Multimeter

Important things you should know

It is important to know that the tinyFISH FC can NOT be powered by the USB port!
It can only be configured over the USB port when power is connected to the power input tabs.  Make sure to have an eye on your Lipo voltage! A full equipped copter with camera and VTX can easily draw 400mA in idle mode…

The whole procedure described below assumes that the FC is NOT yet connected to any hardware. This is just the basic first flashing and testing procedure. Remove all ESCs or camera connections!

Short circuit?

So first of all we are going to verify that there is no hard short circuit. Take your multimeter and measure the resistance between IN- and IN+. Your multimeter should read >1k Ohm. Fine. If it reads <10 Ohms you definitively have a short circuit somewhere. Abort here and recheck your assembly!

When the check is passed take your lab power supply and set it to 4.0V and limit the max current to 0.2A. Now connect the Lab supply to IN- and IN+. The FC should draw <0.1A. If the power supply goes into current limiting mode you have a short somewhere, abort!

DFU?

Next, remove the power and short the BOOT jumper next to the STM32 by adding a solder blob to the pads. Re-connect the power supply (should still read <0.1A) and connect the USB cable. Your PC should now detect a new device. My Linux box shows the following information in the syslog:

[238917.592020] usb 1-3.1: new full-speed USB device number 74 using ehci-pci
[238917.685044] usb 1-3.1: New USB device found, idVendor=0483, idProduct=df11
[238917.685047] usb 1-3.1: New USB device strings: Mfr=1, Product=2, SerialNumber=3
[238917.685049] usb 1-3.1: Product: STM32  BOOTLOADER
[238917.685051] usb 1-3.1: Manufacturer: STMicroelectronics
[238917.685052] usb 1-3.1: SerialNumber: 205630622033

You could also launch the betaflight configurator, you should see an entry named “DFU” in the port selection tab. If this is not the case or you get USB configuration timeouts please check that the BOOT jumper is bridged and that the 8MHZ quartz is soldered properly.

Firmware!

As of writing this the betaflight configurator does not recognize the tinyFISH FC. A pull request was made and this should be fixed soon. For now you will have to download the tinyFISH firmware manually: betaflight_3.1.0_TINYFISH.hex. In case this release candidate has been removed, browse the whole bf release page and search for the TINYFISH hex file manually.

When the download is completed, open up the firmware tab, click on “Load Firmware [Local]”, and click “Flash Firmware”. The firmware should be flashed within some seconds and the board will reboot and enter normal firmware mode.

You should see a new com port listed in the port selection (on my linux box this is /dev/ttyACM0). Perfect! Disconnect the power and the USB cable and remove the solder blob on the BOOT pads. If it does not show up have a look at the LEDs of the fc. Are they blinking? If they blink 6 times there was a gyro/acc fault — double check the MPU6000 soldering.

First contact!

Now we will have a short look if the basic peripherals are working: Re-connect the power and USB connection. Launch betaflight configurator and connect to the serial port of the FC. Enable expert mode and click on the sensors tab. Wiggle around your FC, both sensors (gyro and accelerometer) should show some movements. Fine, the gyro and accelerometer is working!

Have a look at the battery reading on the top, it should show a value close to the input voltage. You can play around with your lab supply settings, you can safely set it to 8V and have a look at the reading. It should follow the input nicely. You can disconnect now.

That’s it for today! The STM32 has been flashed with betaflight and first tests were passed. You can now safely proceed to the next tutorial on how to flash the CC2500 receiver chip with the OpenSky firmware.