U1
MK1
U2
U6
U4
C28
Capacitance
100nF
C14
Capacitance
27pF
SW1
C1
Capacitance
100nF
C20
Capacitance
10uF
J6
C12
Capacitance
100nF
J3
C3
Capacitance
100nF
L2
Inductance
2.2uH
C8
Capacitance
1uF
C13
Capacitance
27pF
C10
Capacitance
100nF
LED1
Color
Green
C25
Capacitance
100nF
C24
Capacitance
10uF
C16
Capacitance
4.7uF
C6
Capacitance
100nF
C9
Capacitance
100nF
C4
Capacitance
100nF
C17
Capacitance
10uF
C23
Capacitance
100nF
C19
Capacitance
68pF
C2
Capacitance
100nF
C27
Capacitance
100pF
C5
Capacitance
100nF
SW2
C7
Capacitance
100nF
C18
Capacitance
100nF
C26
Capacitance
100nF
C11
Capacitance
1uF
R2
Resistance
27.4 Ω
EXTERNAL FLASH CIRCUIT
R13
Resistance
68kΩ
CRYSTAL OSCILLATOR
R15
Resistance
10kΩ
Can connect a DHT11 or DHT22 Sensor
R10
Resistance
470 Ω
One-Wire protocol relies on the bus being pulled high by the pull-up resistor when not actively transmitting
Cl = 2(Ccap_load - Cstray)
R9
Resistance
10kΩ
SOLAR POWER INTERFACE
BATTERY CONNECTION
SOLAR PANEL CONNECTION
LoRa MODULE
Line 1
Enables long-range wireless LoRaWAN communication.
R4
Resistance
1kΩ
R19
Resistance
1k5 Ω
TEMP & HUMIDITY CIRCUIT
Pull up resistors
Line 1
R6 and r9 are are pull ups for the SD Card line
Line 2
Line 2
R18
Resistance
1kΩ
R16
Resistance
50 Ω
MAIN CONTROLLER
R11
Resistance
1k5 Ω
Q1 Disconnects SOLAR input when both SOLAR and USB are connected. NOTE: This is a depletion type mosfet
R14
Resistance
6.8kΩ
R8
Resistance
15kΩ
VOLTAGE REGULATOR
RF filter capacitors, C27, should be the closest to the microphone
MOUNTING HOLES
R7
Resistance
2kΩ
R12
Resistance
50 Ω
I_ch = (Vset / Rset) * 900 = 900mA
MICROPHONE CIRCUIT
R17
Resistance
50 Ω
R5
Resistance
5kΩ
R3
Resistance
10kΩ
R6
Resistance
10kΩ
SD CARD CIRCUIT
R1
Resistance
27.4 Ω
USB INTERFACE
+3V3
QSPI_SD0
VUSB
SD_CLK
SD_DATA1
+1V1
LORA_RX
SD_CLK
+3V3
MIC_WS
Decoupling Capacitors
Line 1
Ensure these capacitors are placed as close as possible to the MCU power rail
QSPI_SD3
LORA_NRST
QSPI_SCLK
QSPI_SS
VBAT
VUSB
SD_DATA3
USB_D-
XOUT
+3V3
LORA_NRST
+3V3
+1V1
VSOLAR
SD_DATA0
VSOLAR
SD_CMD
SD_DATA2
DECOUPLING CAPACITORS 1.1V
Line 1
Ensure these capacitors are placed as close as possible to the MCU power rail
XIN
~USB_BOOT
QSPI_SS
SD_CMD
+3V3
+3V3
QSPI_SD0
MIC_SDA
VBAT
+1V1
XIN
DHT_DATA
USB_D+
SD_DATA2
+3V3
VBAT
LORA_TX
SD_DATA1
QSPI_SD2
SD_DATA0
XOUT
SD_DATA3
LORA_RX
QSPI_SD1
QSPI_SD1
+3V3
MIC_WS
USB_D-
DHT_DATA
MIC_SCL
MIC_SDA
+3V3
+3V3
+3V3
QSPI_SD2
QSPI_SCLK
QSPI_SD3
MIC_SCL
LORA_TX
+3V3
USB_D+
D1
J5
J2
Q1
C29
Capacitance
100nF
U5
D4
Color
Red
C15
Capacitance
10uF
J4
U3
C21
Capacitance
100nF
C22
Capacitance
4u7 F
D5
Color
Green
Y1
J1