GFX example very slow - nRF52840

[Raja]

I am working on a new design and i am using ST7789 (240 X 320 pixels) screen with nRF52840, it is working fine. I have followed the code provided in SDK example (big thanks).

But it is painfully slow, is there a way to make it faster considering nRF52840 has a powerful processor and good memory.

Any guidance will be much appreciated. Due to cost and complexity i wanted not to use a secondary processor.

[Simonr]

Hi

The nrfx_spim example uses the extended features of SPI. Can you try to enable NRFX_SPIM_EXTENDED_ENABLED in the sdk_config.h file and set the frequency to spi_config.frequency = NRF_SPIM_FREQ_32M;

Keep in mind that you need to use SPIM instance 3 (SPIM3) in order to support the 16 or 32 MHz frequencies. 

Best regards,

Simon

[Raja]

Hi Simonr,

I tried by updating code as shown below, but after updating it stopped working. What is it that i am doing wrong?

-->ST7789.c

---------------------------------

#include "nrfx_spim.h"

#define SPI_INSTANCE 3
static const nrfx_spim_t spi = NRFX_SPIM_INSTANCE(SPI_INSTANCE);

//static const nrf_drv_spi_t spi = NRF_DRV_SPI_INSTANCE(ST7735_SPI_INSTANCE);

static ret_code_t hardware_init(void)
{
ret_code_t err_code;

nrf_gpio_cfg_output(ST7789_DC_PIN);

nrfx_spim_config_t spi_config = NRFX_SPIM_DEFAULT_CONFIG;
spi_config.frequency = NRF_SPIM_FREQ_32M;
spi_config.ss_pin = ST7789_SS_PIN;
spi_config.miso_pin = ST7789_MISO_PIN;
spi_config.mosi_pin = ST7789_MOSI_PIN;
spi_config.sck_pin = ST7789_SCK_PIN;
//spi_config.dcx_pin = NRFX_SPIM_DCX_PIN;
spi_config.use_hw_ss = true;
spi_config.ss_active_high = false;
APP_ERROR_CHECK(nrfx_spim_init(&spi, &spi_config, NULL, NULL));
return err_code;
}

-->pca10056\blank\config\sdk_config.h

---------------------------------

#ifndef NRFX_SPIM3_ENABLED
#define NRFX_SPIM3_ENABLED 1
#endif

#ifndef NRFX_SPIM_EXTENDED_ENABLED
#define NRFX_SPIM_EXTENDED_ENABLED 1
#endif