STM32BusIORegister Class Reference

Represents one addressable, read-only, MSB-first register accessed over an STM32SPIDevice, using the "set the top address bit to read" convention (Adafruit_BusIO's ADDRBIT8_HIGH_TOREAD) – e.g. the TSC2046's control byte, whose own START bit already occupies that same top bit, so the OR this class performs is a documented no-op for that specific chip, but is kept for fidelity with the reference API and in case a future chip using this same addressing convention needs the OR to actually do something. More...

#include <STM32BusIORegister.hpp>

Public Member Functions
	STM32BusIORegister (STM32SPIDevice *spiDevice, uint32_t regAddr, size_t width=1, size_t addressWidth=1)
	Constructs a view over one register.
uint32_t	read ()
	Sends the (address-bit-set) register address, then reads back width bytes MSB-first and returns them as a single value.

Detailed Description

Represents one addressable, read-only, MSB-first register accessed over an STM32SPIDevice, using the "set the top address bit to read" convention (Adafruit_BusIO's ADDRBIT8_HIGH_TOREAD) – e.g. the TSC2046's control byte, whose own START bit already occupies that same top bit, so the OR this class performs is a documented no-op for that specific chip, but is kept for fidelity with the reference API and in case a future chip using this same addressing convention needs the OR to actually do something.

A new instance is meant to be constructed on the stack for each register access (matching the reference library's own usage pattern) – it is a thin, stateless-between-calls view over an existing STM32SPIDevice, not a long-lived owned resource.

Warning

Not thread-safe or ISR-safe, for the same reason as STM32SPIDevice: read() ultimately calls STM32SPIDevice::writeThenRead(), which is itself not synchronized.

Definition at line 47 of file STM32BusIORegister.hpp.

Constructor & Destructor Documentation

STM32BusIORegister()

STM32BusIORegister::STM32BusIORegister	(	STM32SPIDevice *	spiDevice,
		uint32_t	regAddr,
		size_t	width = 1,
		size_t	addressWidth = 1 )

Constructs a view over one register.

Parameters

spiDevice	The bus to read this register over. Must outlive this object.
regAddr	The register address/command byte. Only the low addressWidth bytes are used.
width	Number of data bytes to read back, MSB-first. Currently only width == 2 is exercised (by TSC2046), but any width up to 4 is supported since read() accumulates into a uint32_t exactly like the reference library.
addressWidth	Number of address bytes to send. TSC2046 (and every other user of this addressing mode so far) uses 1.

Definition at line 14 of file STM32BusIORegister.cpp.

Member Function Documentation

read()

uint32_t STM32BusIORegister::read

(

)

Sends the (address-bit-set) register address, then reads back width bytes MSB-first and returns them as a single value.

Return values

The	register value, or 0xFFFFFFFF if the underlying SPI transaction failed.

Definition at line 18 of file STM32BusIORegister.cpp.

References STM32SPIDevice::writeThenRead().

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The documentation for this class was generated from the following files:

• STM32BusIORegister.hpp
• STM32BusIORegister.cpp