flow_bridge.h File Reference

ACwing Flow rev A optical-flow bridge (STM32C011 at 0x3B, PMW3901 behind it). More...

#include <stdint.h>
#include "sensor_bus.h"

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Data Structures
struct	flow_t
struct	flow_frame_t

Macros
#define	FLOW_BRIDGE_ADDR_7BIT   0x3Bu
#define	FLOW_BRIDGE_WHO_AM_I   0xF1u
#define	FLOW_REG_WHO_AM_I   0x00u
#define	FLOW_REG_VERSION   0x01u
#define	FLOW_REG_FRAME   0x02u
#define	FLOW_FRAME_LEN   11u
#define	FLOW_REG_CTRL   0x10u
#define	FLOW_ST_SENSOR_OK   0x01u
#define	FLOW_ST_NEW   0x02u
#define	FLOW_ST_OVERFLOW   0x04u
#define	FLOW_ST_REJECTED   0x08u

Functions
int32_t	flow_init (flow_t *f, const sensor_bus_t *bus)
	0 = bridge found
int32_t	flow_read (flow_t *f, flow_frame_t *fr)
	1 = new data, 0 = none, <0 error
void	flow_decode (const uint8_t raw[FLOW_FRAME_LEN], flow_frame_t *fr)
	pure decoder (host tests)

Detailed Description

ACwing Flow rev A optical-flow bridge (STM32C011 at 0x3B, PMW3901 behind it).

The bridge reads the PMW3901 motion burst at 100 Hz over SPI and serves the accumulated motion over I2C. Bridge firmware: 01 - FLOW_FW (its flow_regs.h holds the same map; its host test checks that the two agree). Without a programmed bridge flow_init() fails and the FLOW sensor bit stays 0.

Register map (8-bit addresses, auto-increment, little-endian):

addr name access content 0x00 WHO_AM_I R 0xF1 0x01 VERSION R bridge firmware version (major << 4 | minor) 0x02 STATUS R bit0 PMW3901 ok (product id checked), bit1 new data since the last FRAME read, bit2 overflow (|dX| or |dY| saturated), bit3 last sample rejected (no surface features: low SQUAL at maximum shutter) 0x03 COUNT R u8, +1 per PMW3901 sample accumulated (wraps) 0x04 DX R i16, counts accumulated since the last FRAME read 0x06 DY R i16 0x08 SQUAL R u8, surface quality of the last sample (0..~170) 0x09 SHUTTER R u16, shutter of the last sample 0x0B DT R u16, time covered by DX/DY, units of 100 us 0x10 CTRL W bit0 soft reset of the bridge, bit1 re-init PMW3901

FRAME = 0x02..0x0C (11 bytes) read in ONE transaction: the bridge latches the frame on the read of 0x02 and clears DX, DY, DT and STATUS.bit1.

Axes (sensor-side view of the flow board): DX along +s, DY along +t. With the frame-C2 mounting (t -> forward) the firmware maps them to the body axes.

Definition in file flow_bridge.h.

Macro Definition Documentation

FLOW_BRIDGE_ADDR_7BIT

#define FLOW_BRIDGE_ADDR_7BIT   0x3Bu

Definition at line 39 of file flow_bridge.h.

FLOW_BRIDGE_WHO_AM_I

#define FLOW_BRIDGE_WHO_AM_I   0xF1u

Definition at line 40 of file flow_bridge.h.

FLOW_REG_WHO_AM_I

#define FLOW_REG_WHO_AM_I   0x00u

Definition at line 41 of file flow_bridge.h.

FLOW_REG_VERSION

#define FLOW_REG_VERSION   0x01u

Definition at line 42 of file flow_bridge.h.

FLOW_REG_FRAME

#define FLOW_REG_FRAME   0x02u

Definition at line 43 of file flow_bridge.h.

FLOW_FRAME_LEN

#define FLOW_FRAME_LEN   11u

Definition at line 44 of file flow_bridge.h.

FLOW_REG_CTRL

#define FLOW_REG_CTRL   0x10u

Definition at line 45 of file flow_bridge.h.

FLOW_ST_SENSOR_OK

#define FLOW_ST_SENSOR_OK   0x01u

Definition at line 47 of file flow_bridge.h.

FLOW_ST_NEW

#define FLOW_ST_NEW   0x02u

Definition at line 48 of file flow_bridge.h.

FLOW_ST_OVERFLOW

#define FLOW_ST_OVERFLOW   0x04u

Definition at line 49 of file flow_bridge.h.

FLOW_ST_REJECTED

#define FLOW_ST_REJECTED   0x08u

Definition at line 50 of file flow_bridge.h.

Function Documentation

flow_init()

int32_t flow_init	(	flow_t *	f,
		const sensor_bus_t *	bus
	)

0 = bridge found

Definition at line 8 of file flow_bridge.c.

References flow_t::bus, FLOW_BRIDGE_WHO_AM_I, FLOW_REG_WHO_AM_I, sensor_bus_t::handle, flow_t::ok, sensor_bus_t::read, and flow_t::version.

Referenced by ext_step().

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flow_read()

int32_t flow_read	(	flow_t *	f,
		flow_frame_t *	fr
	)

1 = new data, 0 = none, <0 error

Definition at line 31 of file flow_bridge.c.

References flow_t::bus, flow_decode(), FLOW_FRAME_LEN, FLOW_REG_FRAME, FLOW_ST_NEW, sensor_bus_t::handle, flow_t::ok, sensor_bus_t::read, and flow_frame_t::status.

Referenced by ext_step().

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flow_decode()

void flow_decode	(	const uint8_t	raw[FLOW_FRAME_LEN],
		flow_frame_t *	fr
	)

pure decoder (host tests)

Definition at line 20 of file flow_bridge.c.

References flow_frame_t::count, flow_frame_t::dt_s, flow_frame_t::dx, flow_frame_t::dy, le16(), flow_frame_t::shutter, flow_frame_t::squal, and flow_frame_t::status.

Referenced by flow_read().

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