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7. External flash in block mode

Motivation

When working with Non-Memory-Mapped Flash memory, such as NAND flash, a driver must be developed in order for TouchGFX to use the assets stored within.

Read more about this topic in the Using Non-Memory Mapped flash for storing images section.

Note
Skip this step if nonaddressable external flash is not relevant for your board bring up.

Goal

The goal of this step is to create a driver that can read a number of bytes from a location in the non-mapped flash memory and store it in an array.

Verification

The verification points for this section are:

Verification PointRationale
Ensure contents of flashEnsure that the contents read from the flash are correct.
Verify performanceEnsure that read performance is in accordance with MCU configuration.

Prerequisites

  • Information about the flash, typically from a datasheet.
  • Information about the connections between the MCU and the external flash.
  • The flash speed.

Do

Typically, the NAND flash is configured via the FMC on your MCU.

Remember to configure the GPIOs that are connected to the flash.

A non-memory-mapped QSPI flash is configured in CubeMX like a memory-mapped QSPI flash.

Code

Write code that can read a number of bytes from a specific address of the Flash. An example of how this might look is provided below. The implementation of the driver depends on your flash chip.

void readNonaddressableFlash(uint32_t from, uint8_t *into, uint32_t n)
{
...
}

uint8_t bytes[1000];

//read external Flash
readNonaddressableFlash(0xab001212, bytes, 1000);

This code will be used later to develop the TouchGFX abstraction layer.