⚡ Signal Flow Diagram
Click any block to see details below.
Power Input
Bat1
Li-Po Battery
JST 2-pin connector
Vbat
3.7 V
3.7 V
MCU / BLE
U3
XIAO nRF52840
Firmware + BLE
SPI master
SPI master
SPI (CS, SCK,
SDI, LDAC)
SDI, LDAC)
PS_CTRL
REG_EN
PS_INV
REG_EN
PS_INV
Signal Chain
U2
MCP4822
Dual 12-bit SPI DAC
Biphasic waveform gen
Biphasic waveform gen
U7
TPS65131
Boost + inverting
converter (+HV / −HV)
converter (+HV / −HV)
Vout A/B
+HV / −HV
Conditioning
U4
AD8278
Diff amp
DAC → diff drive
DAC → diff drive
U6
AP7375
2.5 V LDO
(QV analog ref)
(QV analog ref)
U8
L79L05
−5 V LDO
(−QV op-amp rail)
(−QV op-amp rail)
Output Stage
U9
TL072
Current sense
+ feedback
+ feedback
U1
OPA171
Precision op-amp
current control
current control
RN1
R-Network
Sets stim current
magnitude
magnitude
Stim
current
current
Electrode
Stim1
Stim Output
JST 2-pin
Electrode leads
Electrode leads
🔌 MCU Pin Assignments
| Signal | MCU Pin | nRF Pad | Type | Connected To | Description |
|---|