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LPC1769/LPCOpen: SPP Interface with Microchip SPI Flash

Question asked by on Oct 29, 2018
Latest reply on Nov 18, 2018 by Kerry Zhou


I'm trying to interface an SPI Flash memory from Microchip (SST25VF080B-50-4C; datasheet attached) using the SSP interface of the LPC1769 LPCXpresso board. I'm using the LPCOpen library. Initially I would like to issue simple blocking commands and get some fixed responses out of the chip. For instance issuing the JEDEC READ-ID command (0x9F; page 16) should return a fixed response of 3 bytes: [0xBF, 0x25, 0x8E]. However no matter what I do I'm getting [0xBE, 0x19, 0xF8]. Same thing happens with the Read Status Register command (0x05; page 14) which on powerup should return 0b00111000 (0x38); instead it returns 0b00011000 (0x18).


My connections are as follows

  • Vdd: 3V3 and Vss: GND
  • HOLD#: Driven HI; functionality not needed
  • SCK: To LPC1769 SCK1 (p7)
  • SO: To LPC1769 MISO1 (p6)
  • SI: To LPC1769 MOSI1 (p5)
  • WP#: Driven HI; software controlled
  • CE#: To LPC1769 P0.28

I've connected CE# to a GPIO instead of SSEL1 since CE# seems to be pulled HI after every byte transferred instead at the end of the sequence. This causes the memory to reset the command.  Do you have any guidance on how to proceed? Of course it is entirely possible that I missed something fundamental, the newbie that I am. This is a snippet of my code so far. I've tried altering the SCK frequency to values from 100 kHz (default) up 24 MHz with the same results.


#include "board.h"
#define LPC_SSP     LPC_SSP1
/* The JEDEC READ-ID cmd */
static uint8_t JRDID[1] = { 0x9F };
/* Buffer to hold the 1 byte response */
static uint8_t rx_buf[1];

void print_buffer(uint8_t *buf, uint8_t len) {
    for (int i=0; i < len; i++) {
        char byte[16];
        sprintf(byte, "%x", buf[i]);
        DEBUGSTR(" ");

int main(void) {

    Chip_GPIO_SetPinDIROutput(LPC_GPIO, 0, 22);
    Chip_GPIO_SetPinDIROutput(LPC_GPIO, 0, 28); /* for CE */
    Chip_GPIO_SetPinState(LPC_GPIO, 0, 22, true);
    Chip_GPIO_SetPinState(LPC_GPIO, 0, 28, true);

    ssp_format.frameFormat = SSP_FRAMEFORMAT_SPI; /* SPI */
    ssp_format.bits = SSP_BITS_8; /* 8 bits per frame */
    ssp_format.clockMode = SSP_CLOCK_MODE0; /* MODE0; CPHA=0; CPOL=0 */
    Chip_SSP_SetFormat(LPC_SSP, ssp_format.bits, ssp_format.frameFormat,
    Chip_SSP_SetMaster(LPC_SSP, 1);

    /* Pull CE# LO */
    Chip_GPIO_SetPinState(LPC_GPIO, 0, 28, false);
    /* Write JRDID - 1 byte */
    Chip_SSP_WriteFrames_Blocking(LPC_SSP, JRDID , 1);
    /* Read 1 byte into rx_buf */
    Chip_SSP_ReadFrames_Blocking(LPC_SSP, rx_buf, 1);
    /* Pull CE# HI */
    Chip_GPIO_SetPinState(LPC_GPIO, 0, 28, true);
    print_buffer(rx_buf, 1);

I'm using separate WriteFrames and ReadFrames since they will clear the dummy read/write data from the FIFO. But the results are the same with the RW function.