★ N.I.C. ★
Design-stage concept — nothing built. The figures are verified against the parts' sheets and the parts before a board is made.
Ceres measures soil volumetric water content at a WMO reference depth, and the soil temperature
there: ModBus type 6, a MOD on a Palatine arm. A comb electrode on the board's underside reads
through 1 mm of borosilicate glass — the board is potted in a borosilicate bowl, comb down, glass
on both faces — and is read as an admittance at three frequencies: the quadrature part is the
water, the in-phase part the ions, and the frequencies separate the two. The unit answers a
finished, compensated value. Several units lie in the ground in a patrona, a tube packed on the
bench and knocked into the ground as one piece (../palatine/CONSTRUCTION.md, The soil column),
which is what makes the depth repeatable between stations.
| class | house MOD — a Modbus RTU slave on a Palatine arm, ModBus type 6, address 6«2 | NUMBER, 0x18 for unit 0; no clock, the host stamps the reading when it polls |
| what it reports | the water content on 0x0000, the soil temperature at the depth on 0x0001 — one unit, one address, two values (MODBUS.md) |
| the sensing element | the board's own comb under the bowl's glass, horizontal in the patrona's packed sand, glass down |
| the read | a synchronous detector at 2²⁰ / 2²² / 2²⁴ Hz — 1,05 / 4,19 / 16,8 MHz — against a reference capacitor through the same chain (HARDWARE.md) |
| the parts | STM32H523VE · THS4541 · 3× 74LVC1G3157 · 74LVC1G17 · TMP117 or STS35 · THVD1450 · LMR43610 |
| depths | the standard series 5 · 10 · 20 · 50 · 100 cm — the station's pair −10 and −50 cm, a farm's profile −10 · −20 · −50 · −100 cm; which depths a station carries is a crop-and-site decision |
| feed | the arm's isolated 12 V on the four-wire cable, like every sensor on the arm; the board makes its own 3,3 V |
| the cable | flat, four conductors, soldered to the board and potted through the bowl's channel; no connector on the unit |
Sakura is the same board in the same bowl, hung in the canopy — sakura/.
a Palatine arm ── A · B · 12 V · GND ── the flat cable, up the patrona
│
┌────┴─────────────────────────────────────────────────────────────────────────┐
│ CERES — the board potted in a borosilicate bowl │
│ H523 · THVD1450 · the detector chain │
│ the comb on the underside ── 1 mm of glass ── the packed sand at the depth │
│ the thermometer on the board ── the soil temperature there │
└──────────────────────────────────────────────────────────────────────────────┘
ceres/ Ceres — soil moisture and the soil temperature at its depth ModBus 6
└── sakura/ Sakura — leaf wetness, Ceres's board in the same bowl ModBus 7
| file | contents |
|---|---|
HARDWARE.md |
the board and the bowl — the measurement, the chain, the rails, the potting, every pin, the parts, the bench criteria; the one board of Ceres and Sakura |
FIRMWARE.md |
the firmware, described — the read cycle at three frequencies, the admittance arithmetic, the curve and the compensation, what is tested |
MODBUS.md |
the ModBus contract of both units |
WHY.md |
the graveyard |
sakura/ |
Sakura — the same board as the leaf-wetness sensor |
Hardware: CERN-OHL-P v2 (../LICENSE-HW) · Software: MIT (../LICENSE) — Copyright (c) 2026 NIC — Native Intellect Community