topic Re: About SPI for LPC552x in LPC Microcontrollers

About SPI for LPC552x

yuto — Wed, 23 Apr 2025 01:31:51 GMT

I am using LPC552x series.
I am planning to use GPIO as SPI and connect to Flash ROM.
I want to connect two devices to the Flash ROM. Therefore, I want to make the SPI of the LPC552x as high impedance when it is not communicating so that the IO signals do not collide on the board.
Is it possible to set the output signal IO to high impedance when SPI communication is not used?

Re: About SPI for LPC552x

Harry_Zhang — Wed, 23 Apr 2025 08:40:17 GMT

Hi @yuto

Yes, it is possible to configure the LPC552x GPIO pins (used for SPI) as high impedance (Hi-Z) when not actively communicating.

When SPI communication is not active, reconfigure the SPI pins as GPIO inputs. GPIO inputs are naturally high impedance.

Harry

Re: About SPI for LPC552x

yuto — Wed, 23 Apr 2025 08:48:57 GMT

Hi, Harry

Thank you for your response.
Glad to hear that it can be GPIO when SPI is not active.
Can you give me a specific example (program code) to dynamically change the SPI and GPIO settings in a program?

Re: About SPI for LPC552x

Harry_Zhang — Thu, 24 Apr 2025 07:42:36 GMT

Hi @yuto

I think you can refer to the lpc55s28 gpio_led_output demo.

When you want to disable SPI temporarily.

Reconfigure SPI pins.

gpio_pin_config_t spi_config = { kGPIO_DigitalInput, 0, }; GPIO_PinInit(GPIO, APP_BOARD_TEST_LED_PORT, APP_BOARD_TEST_LED_PIN, &spi_config);

Harry

Re: About SPI for LPC552x

yuto — Fri, 25 Apr 2025 00:56:07 GMT

Hi, Harry

Thank you for your response.
I will check the sample as well.