Crazyflie 2 deck carrier

Rev 0.1A

Schematic: here

Gerbers: here

License: CC BY 4.0.
Additionally, if you use this design for scientific work, please add a footnote or reference to this webpage:
Tom van Dijk (2020). Crazyflie 2 deck carrier. Micro Air Vehicle Lab (MAVLab), TU Delft. Retrieved from https://github.com/tomvand/cf-deck-carrier

This carrier board lets the Crazyflie 2 decks by Bitcraze AB be carried by other drones. The board functions similarly to a breakout board but with additional functions. The board is originally designed for the Eachine Trashcan, but may also be useful for other drones.

Nearly all of the features on this carrier board are optional, unused components can be left out to save weight and assembly time. Refer to the optional features section below to check which components should be installed for your application.

Interface

The carrier board should be connected to an autopilot using the connectors J1 to J5. The connectors are grouped by function. In nearly all cases the board can be connected directly to the corresponding autopilot pins.

PWR (J1):

• VCOM provides power to this board and the decks. VCOM does not need to be regulated.
• VUSB is a power supply to the drone, for instance using the Qi charging deck.

UART (J2):

SPI (J3):

• The IO pins on J5 are typically used as Chip Select.

I2C (J4):

IO (J5):

• IO functionality can be replaced by the on-board I2C-to-GPIO and I2C-to-1-Wire bridges for controllers with few free pins.

AUX (J6):

• The auxiliary UART is connected directly to either UART1 or UART2.

Bill of materials

Ref	Qnty	Value	Cmp name	Footprint	Approx. total cost / 5
PCB,	1				€ 4.57
					------------------------
Subtotal					€ 4.57
					------------------------
C1,	1	1uF	C	0805	€ 0.20
C2,	1	10nF	C	0805	€ 0.20
C3,	1	4.7uF	C	0805	€ 0.20
C4, C5,	2	0.1uF	C	0805	€ 0.40
R1, R2, R3,	3	2.2k	R	0805	€ 1.20
					------------------------
Subtotal					€ 2.20
					------------------------
U1,	1	LP2985-3.0	LP2985-3.0	SOT-23-5	€ 3.70
U2,	1	PCA9536D	PCA9536D	SOIC-8	€ 7.15
U3,	1	DS2484	DS2484	SOT-23-6	€ 3.35
					------------------------
Subtotal					€ 14.20
					------------------------
J1,	1	PWR	Molex PicoBlade 1x3 Horizontal Through-hole 53048-0310		€ 1.55
J2,	1	UART	Molex PicoBlade 1x4 Horizontal Through-hole 53048-0410		€ 1.85
J3,	1	SPI	Molex PicoBlade 1x3 Horizontal Through-hole 53048-0310		€ 1.55
J4,	1	I2C	Molex PicoBlade 1x2 Horizontal Through-hole 53048-0210		€ 1.25
J5,	1	IO	Molex PicoBlade 1x5 Horizontal Through-hole 53048-0510		€ 1.90
J6,	1	UART_AUX	Molex PicoBlade 1x4 Horizontal Through-hole 53048-0410		€ 1.85
P1,	1	CF_EXP_LEFT	BF090-10-X-B2		€ 6.60
P2,	1	CF_EXP_RIGHT	BF090-10-X-B2		€ 6.60
SW1,	1	CAS-220	CAS-220B1		€ 9.20
					------------------------
Subtotal					€ 32.35
					------------------------
Total					€ 53.32 / 5

Ordering information

PCB

• PCB size: 33x28mm
• PCB layers: 4
• Silkscreen: both sides
• Min. Trace/Space: 6 mil
• Min. Drill: 15 mil

Find the gerber files here.

PCB manufactoring cost: ~€4.57 / 5 (excl. shipping cost, at JLCPCB, estimated by pcbshopper on Wednesday May 20th 2020)

PCB with partial assembly

SMT assembly files for JLCPCB: here.

PCB manufacturing + (partial) assembly and component cost (basic parts: all C, R)

	Cost / 5
Assembly incl. component cost	€ 15.19
Remaining components	€ 46.55
	----------
Total	€ 61.74

PCB manufacturing + (partial) assembly and component cost (basic + extended parts: all C, R, U)

	Cost / 5
Assembly incl. component cost	€ 29.87
Remaining components	€ 32.35
	----------
Total	€ 62.22

(excl. shipping cost, assembly at JLCPCB; Wednesday May 20th 2020)

Assembly

Recommended soldering order:

1. Passives (C, R)
2. ICs (U)
3. Switch (SW)
4. Headers (P)
5. Connectors (J)

Optional features

Molex Picoblade connectors

Components: J1 to J6

The PCB is designed for through-hole Molex Picoblade connectors. Unused connectors can be left out to save weight. Wires can also be soldered directly to the connector pads for permanent connections.

Voltage regulator

Components: U1, C1, C2, C3

The carrier board includes a voltage regulator that supplies 3.0V at max 150mA. Input voltage VCOM can be ≤16V, although compatibility with the crazyflie decks should be checked!

For autopilots that already supply regulated 3.0V on VCOM, the voltage regulator can be replaced by a solder bridge between VCOM (pad 1) and VCC (pad 5) of U1 (marked by white line).

I2C Pull-ups

Components: R1, R2

The board has space for I2C pull-up resistors (0805) (R1, R2) if these are not present on the autopilot.

I2C-to-GPIO

Components: U2, C4

For drones with a limited number of free pins, the I2C-to-GPIO bridge U2 can be installed to drive the decks' IO pins. Since most of the IO pins serve as Chip Select for SPI communication, software drivers should take care that the I2C/GPIO operation is completed before SPI communication begins.

The IO inputs on the IO connector should not be used if the I2C-to-GPIO bridge is in use.

I2C-to-1-Wire

Components: U3, R3, C5

For drones with a limited number of free pins, the I2C-to-1-Wire bridge U3 can save another pin by routing 1-Wire data over the existing I2C lines. Note that most decks only use 1-Wire for identification and that not all autopilots support this feature. (Paparazzi, for instance, does not.)

The OW input on the IO connector should not be used if the I2C-to-1-Wire bridge is installed.

Auxiliary connector

Components: J6, SW1

The AUX connector J6 can be used to connect another board to the carrier deck. The AUX connector provides unregulated power (VCOM) and a UART bus. Using switch SW1, the auxiliary UART can be connected to UART1 or UART2, depending on the decks that are in use.

For permanent installations, switch SW1 can be replaced by solder bridges between the relevant pads.