Wi-Fi CSI on a Raspberry Pi: capture node, analysis host, Pi 5 compatibility and capacity planning

By Wu Jun · Updated 2026-10-29 · 6 min read

"Can a Raspberry Pi do CSI?" has no single answer. It can be:

1. a Nexmon CSI capture node, where the Pi's own Broadcom radio is taken over by a firmware patch and emits CSI;
2. an analysis host for router CSI, where an MT6000 or another router captures and the Pi only receives UDP, stores data, computes features and serves an API.

The hardware requirements, risks and capacity plans are completely different. Choose the role before buying a card or installing an OS.

0. One-minute decision

1. Role A: the Pi is the CSI capture node

The official support matrix lists Raspberry Pi 3B+, 4B and 5 as typical bcm43455c0 devices ^[1]. Nexmon is a per-frame CSI extraction platform with a peer-reviewed description ^[2].

But "the model is in the table" is only the first check. Real risks include:

• a firmware/kernel mismatch can break the build or networking;
• capture releases wlan0 from NetworkManager, so wireless SSH disappears;
• Pi 5 needs a non-16K-page kernel;
• the modern Makefile.rpi route requires nexutil to be built with USE_VENDOR_CMD=1;
• failed rollback may require the spare SD card or a card reader.

The exact commands and acceptance checks live in the Nexmon CSI practical guide; they are intentionally not duplicated here because they change more often than the role-selection advice.

1.1 Six prerequisites

2. Data quality in Role A

A Nexmon 80 MHz packet does not contain "256 subcarriers, all useful." It contains guard, null and pilot slots. The upstream README publishes the invalid indices for each mode; remove or mask them before analysis.

An 80 MHz receiver can also receive frames occupying only a 20 MHz part of the channel. If most CSI slots are near zero, check the transmitter's actual bandwidth and frame type before blaming the receiver.

Recommended acceptance path:

# Capture 10 seconds first; do not start a 10-minute run if this is empty
sudo tcpdump -i wlan0 dst port 5500 -w csi-10s.pcap
sudo tcpdump -r csi-10s.pcap | wc -l

# Then decode with CSIKit/csiread and report usable subcarriers, packet gaps and chip format

The parsers CSIKit ^[3] and csiread ^[4] are useful references. Record capture duration, UDP packet count, CSI slot count, usable-subcarrier ratio, p95/max packet gap, transmitter bandwidth and MAC filter.

3. Role B: the Pi is the analysis host for router CSI

This is usually much more stable than converting the Pi's own radio:

MT6000 / router                        Raspberry Pi
CSI daemon  -- UDP/LAN -->  csi_capture.py / tcpdump
                                  |
                                  +-- raw bin/pcap
                                  +-- Python features
                                  +-- MQTT / REST
                                  +-- heatmaps / Home Assistant

The Pi never patches router firmware. It only runs network services. If the analysis process crashes, the home network and the capture source remain independently recoverable.

3.1 Calculate the real data volume

Do not infer storage from "the network is gigabit." Count actual records or UDP packets:

bytes/s ≈ records/s × bytes/record + IP/UDP/pcap overhead

This project's public MT6000 capture provides a verifiable reference: 57,293 chain records and 60,612,922 bytes for about 600 seconds ^[5], or:

60,612,922 / 599.924 ≈ 101 KB/s
60,612,922 / 10 min  ≈ 347 MB/hour

The published 10-minute archive is about 58 MB; the difference is decimal versus binary display. For higher record rates:

The last row requires eight independent core/stream sources. Do not multiply ordinary frame rate by eight. Measure actual record size, packet count and file growth before deployment.

3.2 Hardware and network budget

For continuous recording, USB SSD storage is generally more appropriate than high-frequency writes to an SD card. Monitor storage health and keep a manifest/SHA-256 record ^[6].

4. Recommended deployment order

1. Install 64-bit Raspberry Pi OS Lite and connect Ethernet;
2. assign a fixed LAN address; never expose UDP 5500 or the management API to the internet;
3. install Python, NumPy, capture tools and the project toolkit ^[6];
4. validate the parser with a local sample or the public 10-second file before waiting for router traffic;
5. receive 10 seconds of UDP and inspect file growth and record count;
6. extend to 10 minutes and record maximum gaps, disk headroom, CPU and temperature;
7. add systemd supervision, log rotation and low-disk alerts;
8. connect MQTT/REST/Home Assistant only after the capture path is stable.

Minimum verification:

# 1) confirm UDP arrives
sudo tcpdump -ni eth0 udp port 5500 -c 20

# 2) record 10 seconds and inspect file growth
sudo tcpdump -ni eth0 udp port 5500 -w csi-10s.pcap

# 3) use the project parser to report records, duration and gaps
python3 scripts/analyze_csi_capture.py csi-10m.bin --outdir analysis

The interface name, record format and daemon port must match your router configuration.

5. Reliability and privacy in Role B

• One-way LAN ingest: the Pi receives UDP; it does not initiate internet access to the router;
• Process isolation: run analysis under a dedicated non-root user;
• Data minimisation: retain only the target device MAC and anonymise before publication;
• API authentication: add authentication and firewall rules before crossing network boundaries;
• Retention policy: keep raw captures, features and graphs in separate retention classes;
• Recovery drill: reboot the Pi and confirm the receiver automatically resumes;
• Consent: CSI can reveal human activity; inform household members and do not use it for covert surveillance.

The field survey by Ma et al. provides a broader view of CSI sensing capabilities and limits ^[7]. A Pi and one radio cannot prove identity, medical status or through-wall imaging from a single stream.

6. Production acceptance checklist

7. When not to use a Raspberry Pi

• If you only need to inspect this site's dataset, a normal computer is faster;
• for one-room presence detection, an ESP32 + ESPHome node costs less;
• if the MT6000 already captures CSI, run the tested daemon directly on the router;
• for medical, security or unattended alarm claims, one low-rate sensor is not enough; add independent sensing and human review.

Continue with the full Nexmon capture-node guide, MT6000 reproduction, 10-minute dataset or tools and scripts.