Stores the touch calibration matrix in the MB85RS64V FRAM and checks it when loading. More...

#include "Adafruit_RA8875.h"
#include "MB85RS64V.hpp"

Functions
void	touchCalibrationAttachStorage (Adafruit_RA8875 display, MB85RS64V fram)
	Registers the FRAM read and write callbacks with the display library.

bool	touchCalibrationLoad (Adafruit_RA8875 display, MB85RS64V fram, tsMatrix_t *matrix)
	Loads the calibration matrix from the FRAM if a valid one is stored.

bool	touchCalibrationSave (Adafruit_RA8875 display, MB85RS64V fram, tsMatrix_t *matrix)
	Saves the calibration matrix to the FRAM and checks it by reading it back.

Variables
constexpr uint16_t	TOUCH_CAL_ADDRESS = 0x0100
	FRAM address of the calibration matrix block written by the RA8875 library.

constexpr uint16_t	TOUCH_CAL_HEADER_ADDRESS = 0x0120
	FRAM address of the 12-byte validity header.

Detailed Description

Stores the touch calibration matrix in the MB85RS64V FRAM and checks it when loading.

Project: F439_CPP_SPI_RA8875_TFT_LCD_04

The matrix itself is written and read by the RA8875 library (Adafruit_RA8875::writeCalibration()/readCalibration()), which calls back into this module to reach the FRAM. On top of that this module keeps a small header with a magic number, a version, the block length and a CRC-32 of the stored matrix bytes. The header is written last, after the matrix, so a power failure part-way through a save leaves a header that does not match the data and the next start simply calibrates again. A blank FRAM (all 00 or all FF), a damaged matrix, a different format version and a zero divider are all treated as "no valid calibration".

FRAM layout (all addresses inside the MB85RS64V's 8192 bytes):

TOUCH_CAL_ADDRESS (0x0100), 29 bytes: the library's matrix block (seven 32-bit values, most significant byte first, then a "calibrated" flag byte)
TOUCH_CAL_HEADER_ADDRESS (0x0120), 12 bytes: magic "CAL1", version, length, CRC-32

Warning: Thread safety: not thread-safe and not ISR-safe. Every function here is a sequence of separate FRAM transactions on a bus shared with the display; save() is several of them in a row and only the last one marks the data as valid. A second caller that used the FRAM or the SPI bus in between could corrupt the sequence. Call from one thread only, while nothing else uses SPI1.

Created on: Oct 5, 2026 Author: johng

Definition in file touchCalibrationStorage.hpp.

Function Documentation

◆ touchCalibrationAttachStorage()

void touchCalibrationAttachStorage	(	Adafruit_RA8875 *	display,
		MB85RS64V *	fram )

Registers the FRAM read and write callbacks with the display library.

Parameters

display	The RA8875 display object.
fram	The started MB85RS64V driver that holds the calibration.

Must be called once before touchCalibrationLoad() or touchCalibrationSave(). If either pointer is null it prints the reason and calls Error_Handler(), which does not return.

Definition at line 94 of file touchCalibrationStorage.cpp.

References Adafruit_RA8875::setCalibrationStorage(), and MB85RS64V::SIZE_BYTES.

Referenced by initTouchCalibration(), and testTouch().

◆ touchCalibrationLoad()

bool touchCalibrationLoad	(	Adafruit_RA8875 *	display,
		MB85RS64V *	fram,
		tsMatrix_t *	matrix )

Loads the calibration matrix from the FRAM if a valid one is stored.

Parameters

display	The RA8875 display object, with the storage attached.
fram	The started MB85RS64V driver.
matrix	Receives the matrix when the function returns true.

Returns: true if a valid calibration was found (magic, version, length, CRC and the library's flag all agree and the divider is not zero); false if none is stored or it is damaged, in which case the reason is printed and the caller should calibrate again. A failed SPI transfer is not reported here: the FRAM driver calls Error_Handler().

Definition at line 114 of file touchCalibrationStorage.cpp.

References tsMatrix_t::Divider, MB85RS64V::read(), Adafruit_RA8875::readCalibration(), TOUCH_CAL_ADDRESS, and TOUCH_CAL_HEADER_ADDRESS.

Referenced by initTouchCalibration(), and touchCalibrationSave().