486 BioPulse Tile
486 : BioPulse Tile
- Author: Roberto Medina
- Description: A tiny vital-sign radar event detector: tracks an 8-bit signal baseline, detects breathing cycles, and flags normal/fast/slow/irregular breathing and apnea.
- GitHub repository
- Open in 3D viewer
- Clock: 1000 Hz
How it works
BioPulse Tile turns a single 8-bit radar/biosignal sample stream into vital-sign events and metrics, using only digital logic — no CPU, no software. The datapath processes one sample per clock.
Processing chain:
- Input select — the 8-bit
ui_insample, or, in demo mode (uio[0]=1), an internal generator producing a synthetic breathing triangle plus a small heartbeat ripple. - Baseline tracker — a slow exponential moving average (alpha = 1/256) estimates the DC level; a faster EMA (alpha = 1/2) high-passes the signal to isolate the heartbeat band.
- Breathing detector — a hysteresis comparator against
baseline ± thrmarks one breath per low→high crossing.uio[1]selects sensitivity. - Classification FSM — labels the breathing period normal / fast / slow / irregular, or raises apnea after 255 clocks with no breath.
- Heartbeat detector — a second hysteresis path on the high-passed signal detects the faster heartbeat component.
- Rate estimators — two sequential long-division units compute
breaths-per-minute and heart-rate as
BPM = 1000 / period. - Signal-quality — peak-to-peak amplitude over each frame gives a quality flag.
- UART transmitter — every frame it streams a 5-byte packet (8N1, LSB
first) out of
uio[5]:0xAA, breaths-per-min, heart-rate, peak-to-peak, flags.
Reading the outputs
uo_out is dual-purpose, selected by uio[2] (BPM readout select):
-
uio[2]=0→uo_outshows the status flags:Bit Meaning 0 breathing detected 1 apnea warning 2 fast breathing 3 slow breathing 4 irregular signal / motion 5 heartbeat detected 6 signal quality good 7 valid / status -
uio[2]=1→uo_outshows the 8-bit breaths-per-minute value.
uio[5] is the UART transmit line; uio[7:6] show the top two bits of
breaths-per-minute as a coarse indicator.
Controls (uio[4:0], inputs)
uio[0] demo mode, uio[1] sensitivity, uio[2] BPM readout select,
uio[4:3] demo pattern (00=normal, 01=fast, 10=slow, 11=apnea).
A note on timing
Periods and thresholds are in clocks. Run the chip at a low clock for realistic vital-sign timescales, or feed external samples at your sample rate.
How to test
Run the cocotb testbench:
cd test
make
It checks reset, the four demo patterns (normal / fast / slow / apnea), the heartbeat detector, the breaths-per-minute readout, UART activity, and external-input mode.
On hardware: set uio[0]=1, pick a pattern on uio[4:3], and watch uo_out
on LEDs (flags). Set uio[2]=1 to read breaths-per-minute on the same LEDs,
and capture uio[5] with a 3.3 V UART receiver to read all the streamed
metrics.
External hardware
None required for the demo. For real measurements, connect the digitised
output of a continuous-wave radar or biosignal analog front-end to
ui_in[7:0], LEDs to uo_out, and optionally a UART receiver to uio[5].
IO
| # | Input | Output | Bidirectional |
|---|---|---|---|
| 0 | sample[0] - 8-bit radar/biosignal sample (external mode) | breathing detected / BPM[0] | demo mode enable (in) |
| 1 | sample[1] | apnea warning / BPM[1] | sensitivity select (in) |
| 2 | sample[2] | fast breathing / BPM[2] | BPM readout select (in) |
| 3 | sample[3] | slow breathing / BPM[3] | demo pattern select [0] (in) |
| 4 | sample[4] | irregular signal / BPM[4] | demo pattern select [1] (in) |
| 5 | sample[5] | heartbeat detected / BPM[5] | UART TX - streams metrics (out) |
| 6 | sample[6] | signal quality good / BPM[6] | coarse breaths-per-min [6] (out) |
| 7 | sample[7] | valid / status / BPM[7] | coarse breaths-per-min [7] (out) |