c - Dump Flash Memory through a single GPIO pin -

i'm working infineon's xmc4500 relax kit , i'm trying extract firmware through single gpio pin.

my naive idea dump 1 bit @ time through gpio pin , somehow "sniff" data logic analyzer.

pseudocode:

while(word word memory copy hasn't finished)   ...   register = value;   temp_value = value , 0x1;   pin = temp_value;   value = value >> 1;   ... 

am on right track? have better/nicer idea how archive this?

### edit ###

actually requirement of (shell)code needs tiny. found this nifty trick on how dump firmware blinking leds.

however i'm struggling receive correct values saleae logic analyzer.

basically i'm doing is:

1. setup gpio pin directions output
2. blink led1 (pin 1.1) clock (spi serial clock)
3. blink led2 (pin 1.0) data bits (spi mosi)
4. sniff pins logic analyzer

here's c code:

#include "xmc4500.h"  #define del 1260  void init()  {   // p1.0 output, push pull   port1->iocr0 = 0x80ul << 0;   // p1.1 output, push pull   port1->iocr0 |= 0x80ul << 8; }  void delay(int i) {    while(--i) {      asm("nop\n");      asm("nop\n");    }  }  // sets pin high // p1.0 = spi mosi // p1.1 = spi clock void output_high(int i) {   // p1.0 high   if(i == 0) {     port1->out |= 0x1ul;     }    // p1.1 high   if(i == 1) {     port1->out |= 0x2ul;   }  }  // sets pin low // p1.0 = spi mosi // p1.1 = spi clock void output_low(int i) {   // p1.0 low   if(i == 0) {     port1->out &= (~0x1ul);   }    // p1.1 low   if(i == 1) {     port1->out &= (~0x2ul);   } }  // spi bit banging void spi_send_byte(unsigned char data) {   int i;    // send bits 7..0   (i = 0; < 8; i++)   {     // sets p1.1 low (serial clock)     output_low(1);      // consider leftmost bit     // set line high if bit 1, low if bit 0     if (data & 0x80)       // sets p1.0 high (mosi)       output_high(0);     else       // sets p1.0 low (mosi)       output_low(0);      delay(del);      // sets p1.1 high (serial clock)     output_high(1);      // shift byte left next bit leftmost     data <<= 1;   } }  int main() {   init();    while(1) {     spi_send_byte('t');     spi_send_byte('e');     spi_send_byte('s');     spi_send_byte('t');   }    return 0; } 

### 2nd edit ###

dumping flash memory working fine following code:

#include "xmc4500.h"  // spi bit banging void spi_send_word(uint32_t data) {   int i;    // lsb first, 32 bits per transfer   (i = 0; < 32; i++)   {     // set pin 1.1 low (spi clock)     port1->out &= (~0x2ul);      // set line high if bit 1, low if bit 0     if (data & 0x1) {       // set pin 1.0 high (spi mosi)       port1->out |= 0x1ul;     }     else {       // set pin 1.0 low (spi mosi)       port1->out &= (~0x1ul);        }      // set pin 1.1 high (spi clock)     port1->out |= 0x2ul;      data >>= 1;   } }  int main() {   // start dumping @ memory address 0x08000000   unsigned int *p;   p = (uint32_t *)(0x08000000u);    // configure pin 1.0 , pin 1.1 output (push-pull)   port1->iocr0 = 0x8080ul;    while(1) {     spi_send_word(*p);     p++;   } } 

the biggest problem solution recovering timing information - knowing 1 word starts , ends. simpler output data on uart tx pin - uart adds start , stop bits , manages timing you, , output can read directly via regular pc serial port.

if cannot use uart, emulating uart bit-banging gpio uart timing still allow conventional serial port used receive data directly.

an example software uart implementation can found here. in case of course need transmit capability.