COSMIIC Pulse Generator (PG4)
The PG4 is a four-channel implantable pulse generator for electrical stimulation of nerve and muscle tissue. It delivers programmable monopolar stimulation through four independent electrodes, using the device case as the common return path.
How it works
The PG4 receives stimulation parameters over the CANopen network from the Power Module. Its Atmel AT90CAN128 processor converts control signals into precise charge-balanced stimulus pulses according to pre-programmed patterns or real-time commands. The SYNC message from the PM controls pulse frequency.
Three independent failsafe mechanisms protect against overstimulation:
- Hardware limits on total charge per pulse
- Software limits on stimulation parameters
- Magnetic shutdown switches in both PG4 and PM
Hardware
| Parameter | Value |
|---|---|
| Processor | Atmel AT90CAN128 (8-bit AVR) |
| Channels | 4 independent monopolar |
| Pulse Width | 1–255 microseconds |
| Pulse Amplitude | 0–20 mA |
| Inter-Phase Interval | 5–100 μs (default 50) |
| Frequency | 1–50 Hz (via SYNC period) |
| Network | CANopen, 4 ports (1 in + 3 out) |
| Power | Network-powered from PM |
| Case | Titanium with epoxy header |
| Placement | Extremities (upper arm, forearm) |
Stimulation Modes
- Direct PM parameter setting — ~50 Hz update, up to 24 channels
- SDO direct setting — ~4 Hz for 12 channels, ~50 Hz single channel (recommended for testing)
- Pattern-based lookup tables — preloaded, up to 48 patterns per PG4 (recommended for permanent systems)
MATLAB Control
nnp.networkOn;
nnp.setSync(50); % 50ms = 20 Hz
nnp.enterTestStim;
nnp.write(node, '3212', ch, [PW, PA*10]); % pulse width, amplitude
nnp.write(node, '3212', ch, [0, 0]); % stop
nnp.enterWaiting;
Build
Source: COSMIIC-Community/Implantables-PG4-Hardware (Aug 2025)
EDA: Altium Designer (PcbDoc + SchDoc format)
Firmware: COSMIIC-Community/Implantables-PG4-App (C, AVR toolchain)
Source
All design files are open source under CERN-OHL-P-2.0 (hardware) and MIT (firmware).
Files
| File | Description |
|---|---|
cosmiic-pg4-altium-project.zip | Altium project — PcbDoc, PcbLib, 8-page schematic (SchDoc), PrjPCB |
cosmiic-pg4-gerbers.zip | Gerber fabrication files |
cosmiic-pg4-schematic.pdf | Full schematic PDF (8 pages) |
cosmiic-pg4-assembly.step | Complete mechanical assembly STEP (titanium case, headers, capthroughs) |
cosmiic-pg4-bom.xlsx | Bill of Materials (Excel) |
Altium Project Structure
The Altium project (PG4D) contains:
- PCB layout (
PG4D.PcbDoc) + component library (PG4D.PcbLib) - 8-page schematic covering stimulation DACs, current sources, CAN interface, AVR MCU, safety circuits, and electrode connectors
NSF Relevance
The PG4 is a four-channel implantable stimulator module capable of delivering programmable monopolar stimulation through four independent electrodes using the device case as the return path. Powered and networked through a single cable, the PG4 incorporates an Atmel AT90CAN128 MCU for precise waveform generation and incorporates triple-layer failsafe protections, including hardware charge limits, software safety checks, and magnetic shutdown control.
Science Drivers
implantable_healthcare
Created by: adonis Version: v1 Category: stimulation