PCB Auto Routing Guide

Here’s how to wire the J2 TF-015 microSD holder in SPI mode to your XIAO header nets:

Table


J2 PinSignal (SPI)Connection
1CS (Chip Select)Connect to a free GPIO on the XIAO. Add a net portal “CS” and tie that to Pin 1. Eg. CS
2CMD (DI / MOSI)XiaoMosi
3VDD (3.3 V Supply)VCC_5V (if you have a 3.3 V regulator, use that net instead)
4CLKXiaoSck
5VSS (Ground)GND net
6DAT0 (DO / MISO)XiaoMiso
7DAT1 (NC in SPI)Leave unconnected (or tie to GND if required)
8DAT2 (NC in SPI)Leave unconnected (or tie to GND if required)
Notes:
  • In SPI mode only DAT0 is used for MISO; DAT1–DAT3 (Pin 1 can double as CD) aren’t needed.
  • Add a 10 kΩ pull-up on CS, CMD and DAT0 lines if your software library requires it.
  • Ensure the card’s VDD matches your regulator (3.3 V); avoid feeding 5 V directly to the card.
Pull-up resistor value
Select bypass capacitor
Label SPI nets
Add pull-up resistor
VCC_5V
VBATT
JP1
C6
Capacitance
1uF
XiaoMiso
VCC_5V
SCK
XiaoRx
C5
Capacitance
10uF
VBATT
C4
Capacitance
10uF
C3
Capacitance
1nF
XiaoSck
XiaoMiso
SDA
C1
Capacitance
10uF
VCC_3.3V
XiaoMosi
C2
Capacitance
10uF
XiaoTx
XiaoSck
XiaoMosi
VCC_3.3V
M3
J1
U2
M4
R27
Resistance
5.1 Ω
R1
Resistance
4.7kΩ
M1
R6
Resistance
1.5kΩ
BT2
J2
R4
Resistance
470 Ω
M2
LED1
U1

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