0966fa8cfc
The firmware has never been flashed, and a real bug already reached the repo because of it: RD03E_FRAME_LEN was 5 for a 6-byte frame, so the footer check collided with the distance high byte and EVERY distance reading was garbage — always `lo | 0x5500`, about 218 metres, regardless of what the sensor saw. That was pure logic with no hardware dependency. It should have been catchable on a laptop, and there was simply no way to run the code. Extracted the hardware-free logic out of the three drivers — rd03e_parse, bmp280_compensate, mems_level — as moves rather than rewrites, carrying the explanatory comments along with the code they explain. The drivers now own only their bus I/O and call into the pure units, so nothing changes for the real device. `./run_tests.sh` builds them with gcc -Wall -Wextra -Werror plus a dependency-free assert harness: 175 checks, 0 failed, from a clean tree. Proven to catch the actual bug rather than assumed to: reintroducing FRAME_LEN 5 fails four checks, including one that reads "a simple-report frame is 6 bytes, not 5", plus the truncated-frame and 5-byte-window cases. Restored, green again. This does NOT make the firmware verified, and the README says so plainly — it is called a narrow exception and scoped to pure logic. Wiring, timing, real register behaviour and the reconstructed RD-03E frame format all still need the physical board. Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
67 lines
2.4 KiB
C
67 lines
2.4 KiB
C
// Bosch BMP280 compensation maths + calibration/ADC decoding — PURE LOGIC.
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//
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// ESP-IDF-free by design: no I2C, no esp_err_t, no FreeRTOS, no logging.
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// Only <stdint.h>/<stddef.h>, so it compiles and is testable on a host
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// with plain gcc (see ../test/). `bmp280.c` does the I2C traffic and calls
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// in here for every byte-order decision and every line of arithmetic.
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//
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// The formulas are Bosch datasheet (rev 1.23) §3.11.3's double-precision
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// reference implementation, transcribed near-verbatim, with the variable
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// names kept close to the original so it's checkable against the datasheet
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// PDF side-by-side. The register map decoded below is §3.11.1.
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//
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// What host tests can prove here: byte-order/packing of the calibration
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// block and the 20-bit ADC words, and that the arithmetic behaves
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// sanely and monotonically. What they CANNOT prove: that this exact
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// silicon returns the register contents we assume.
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#pragma once
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#include <stddef.h>
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#include <stdint.h>
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#ifdef __cplusplus
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extern "C" {
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#endif
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// Calibration block is 24 bytes at 0x88..0x9F (dig_T1..dig_P9).
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#define BMP280_CALIB_LEN 24
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// Burst measurement read is 6 bytes from 0xF7: press(3) + temp(3).
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#define BMP280_RAW_LEN 6
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typedef struct {
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uint16_t dig_T1;
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int16_t dig_T2;
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int16_t dig_T3;
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uint16_t dig_P1;
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int16_t dig_P2;
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int16_t dig_P3;
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int16_t dig_P4;
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int16_t dig_P5;
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int16_t dig_P6;
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int16_t dig_P7;
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int16_t dig_P8;
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int16_t dig_P9;
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} bmp280_calib_t;
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// Decode the 24-byte calibration block. Each coefficient is stored
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// little-endian (LSB first) in the register map.
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void bmp280_calib_from_regs(const uint8_t buf[BMP280_CALIB_LEN], bmp280_calib_t *out);
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// Decode the 6-byte burst read into the two 20-bit ADC words. Pressure
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// comes first (0xF7..0xF9), then temperature (0xFA..0xFC); each is
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// MSB/LSB/XLSB with the XLSB's top nibble carrying the low 4 bits.
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void bmp280_adc_from_regs(const uint8_t raw[BMP280_RAW_LEN], int32_t *out_adc_P, int32_t *out_adc_T);
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// Returns degrees C, and writes the shared `t_fine` intermediate that the
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// pressure compensation needs.
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double bmp280_compensate_temperature(const bmp280_calib_t *c, int32_t adc_T, double *out_t_fine);
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// Returns Pa. Returns exactly 0.0 when the datasheet's own divide-by-zero
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// guard trips (var1 == 0, i.e. an all-zero / unread calibration block).
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double bmp280_compensate_pressure(const bmp280_calib_t *c, int32_t adc_P, double t_fine);
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#ifdef __cplusplus
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}
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#endif
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