MCU installation instructions

Step 1: Cut-down MCU board

The design space inside Airframe A required that the MCU be cut down using shears. The original size and the change in size are shown below.

Step 2: Remove both serial ports

The two serial ports need to be removed since they will not be used and to be able to fit the MCU in the measurement box. The two serial ports can be removed by removing the solder on the back for each serial port using the solder gun and unsolder wire. See Figure below.

Step 3: Modify the 40-pin Ribbon cable

There are 32 parallel I/O controller A signals/pins. A 40 (2x20)-pin single ended header/Ribbon cable will be used to connect the two UART, ADC, and I/O pins on the MCU to the Altimeter, GPS, and Airspeed devices. Since only one single row of the ribbon cable will be plugged into the 32 pins on the MCU, which means that only 20 pins can be used. The two sides of the header cable are thicker than the space between the pins on the MCU. Therefore, the header of the 40-pin cable has to be adjusted so that the two sides of the header can fit between the MCU pins. Two holes of the same size as the MCU pin size can be made on each side end of the header cable using a drill bit and drill press. The Figures below shows the original 40-pin cable and the 40-pin cable with the 2 holes.

Step 4: Connecting 40-pin cable to each device cable

The 40 wires corresponds to the 40 pins that will be fanned out so that each wire corresponds to the pins that will be used, and can be soldered on the corresponding pin of the other devices as shown in the connection diagram. For example, pins PA5 and PA6 on the MCU will be connected to pins 1 and 2 on the Altimeter, respectively as shown in the connection diagram. However, each device has its own type of cable. To connect each wire coming out of the 40-pin cable to each wire coming out of each device cable, 2-plugs cable will be used. As shown in the Figure below, one side goes inside of the other, where one side will be connected to it the MCU pins (40-pin wires) and the other side will be connected to it the pins from the other device. No special tools are required, just a soldering iron to attach the pins. Follow same procedure for each device that will be connected to the MCU except for the IMU.

All the connections are shown in the connection diagram below.

Step 5: Modify the 10-pin Ribbon Cable

The 10-pin UEXT SPI on the MCU will be used to connect the IMU board to the MCU. A 2x5 pin IDC Ribbon cable as shown in the Figure below was used and connected to the UEXT SPI on the MCU. One end of the 2x5 pin Ribbon cable will be removed (cut). This is because there are 12 pins on the IMU board (not 10 pins) and also the size of the pins on the IMU board is different from the size of the MCU pins.

Step 6: connect the MCU to the IMU 12-pin cable

The CONN 12POS 2MM IDC/12-pin socket cable was used for the IMU board and connected to J1. The cable is shown in the Figure below. Each of the five wires corresponds to the pins of the 2x5 pin Ribbon cable that will be connected to the IMU.

This will be pitched in each contact on the 12POS socket cable, which corresponds to pin on the IMU.

Step 7: Modify the GPS 8-pin cable

The 32-channel San Jose Navigation GPS we are using comes with the cable. However, if more cables are needed, SANAV FV-M8 GPS cable (8-pin) can be used. The cable is shown in the Figure below. It is an 8-pin double-ended header cable. One end will be removed, so that each wire can be solder on the MCU as shown in the connection diagram. Follow the same connection procedure from step 4 using the 2-plugs cable.

Step 8: Modify the Altimeter cable

The Altimeter device “Zlog” comes with a USB 4-pin adapter cable, which is shown in the Figure below. NOT COMPLETE!!

Step 9: Modify Airspeed cable

The two lengths of the included small diameter silicon tube, the pressure and static connections of the pitot tube will be used to connect them to the “+” and “-“ ports of the MicroSensor, as shown in Figure 1 below.

The Airspeed device comes with a double-ended header cable. One header side has 4 positions, which will be connected to the Airspeed device, and the other side has 3 positions. See the cable Figure, Figure 2, and Figure 3 below. There are only two wires coming out of the 3 positions side, which will be connected to the ADC on the MCU. On the 4-pin header side, which is connected to the Airspeed, since only two wires are coming out of it, there are 2 slots without any connection. These two slots are used to configure desired units. A wire jumper can be installed connecting the 2-pins for Metric/English switching. After the desired units are configured, disconnect from power and the wire jumper can be removed. The other header end of the cable (2-pin side) will be removed so that the two wires can be soldered on the MCU. Follow same connection procedure from step 4 using the 2-plugs cable.

MCU Connections

MCU Devices

UART0 Altimeter “ZLOG”

UART 1 GPS

SPI (UEXT) IMU

ADC Airspeed

I/O PIN

Power

MCU connection diagram

PA6 => TXD0PA5 => RXD0

2 => RX 1 => TX

4 => GND

PA21 => RXD1PA22 => TXD1

3 => TX1 4 => RX1

2 => GND

7 => MISO8 => MOSI9 => SPCK10 => NPCS12 => GND

(J1) 4 => DOUT (J1) 6 => DIN (J1) 2 => SCLK (J1) 3 => CS (J1) 7 => GND

AD6AD7

“Red” “White” “Yellow” “Brown”

PA25PA26

USB Main Battery 5V (Airframe B)