Add a version of OneWire library adapted for ESP8266

libraries/OneWire/examples/DS250x_PROM/DS250x_PROM.pde

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+/*
+DS250x add-only programmable memory reader w/SKIP ROM.
+ 
+ The DS250x is a 512/1024bit add-only PROM(you can add data but cannot change the old one) that's used mainly for device identification purposes
+ like serial number, mfgr data, unique identifiers, etc. It uses the Maxim 1-wire bus.
+ 
+ This sketch will use the SKIP ROM function that skips the 1-Wire search phase since we only have one device connected in the bus on digital pin 6.
+ If more than one device is connected to the bus, it will fail.
+ Sketch will not verify if device connected is from the DS250x family since the skip rom function effectively skips the family-id byte readout.
+ thus it is possible to run this sketch with any Maxim OneWire device in which case the command CRC will most likely fail.
+ Sketch will only read the first page of memory(32bits) starting from the lower address(0000h), if more than 1 device is present, then use the sketch with search functions.
+ Remember to put a 4.7K pullup resistor between pin 6 and +Vcc
+ 
+ To change the range or ammount of data to read, simply change the data array size, LSB/MSB addresses and for loop iterations
+ 
+ This example code is in the public domain and is provided AS-IS.
+ 
+ Built with Arduino 0022 and PJRC OneWire 2.0 library http://www.pjrc.com/teensy/td_libs_OneWire.html
+ 
+ created by Guillermo Lovato <glovato@gmail.com>
+ march/2011
+ 
+ */
+
+#include <OneWire.h>
+OneWire ds(2);                    // OneWire bus on digital pin 2
+void setup() {
+  Serial.begin (9600);
+}
+
+void loop() {
+  byte i;                         // This is for the for loops
+  boolean present;                // device present var
+  byte data[32];                  // container for the data from device
+  byte leemem[3] = {              // array with the commands to initiate a read, DS250x devices expect 3 bytes to start a read: command,LSB&MSB adresses
+    0xF0 , 0x00 , 0x00   };       // 0xF0 is the Read Data command, followed by 00h 00h as starting address(the beginning, 0000h)
+  byte ccrc;                      // Variable to store the command CRC
+  byte ccrc_calc;
+
+  present = ds.reset();           // OneWire bus reset, always needed to start operation on the bus, returns a 1/TRUE if there's a device present.
+  ds.skip();                      // Skip ROM search
+
+  if (present == TRUE){           // We only try to read the data if there's a device present 
+    Serial.println("DS250x device present");
+    ds.write(leemem[0],1);        // Read data command, leave ghost power on
+    ds.write(leemem[1],1);        // LSB starting address, leave ghost power on
+    ds.write(leemem[2],1);        // MSB starting address, leave ghost power on
+
+    ccrc = ds.read();             // DS250x generates a CRC for the command we sent, we assign a read slot and store it's value
+    ccrc_calc = OneWire::crc8(leemem, 3);  // We calculate the CRC of the commands we sent using the library function and store it
+
+    if ( ccrc_calc != ccrc) {      // Then we compare it to the value the ds250x calculated, if it fails, we print debug messages and abort
+      Serial.println("Invalid command CRC!");
+      Serial.print("Calculated CRC:");
+      Serial.println(ccrc_calc,HEX);    // HEX makes it easier to observe and compare
+      Serial.print("DS250x readback CRC:");
+      Serial.println(ccrc,HEX);
+      return;                      // Since CRC failed, we abort the rest of the loop and start over
+    }
+    Serial.println("Data is: ");   // For the printout of the data 
+    for ( i = 0; i < 32; i++) {    // Now it's time to read the PROM data itself, each page is 32 bytes so we need 32 read commands
+      data[i] = ds.read();         // we store each read byte to a different position in the data array 
+      Serial.print(data[i]);       // printout in ASCII
+      Serial.print(" ");           // blank space 
+    }
+    Serial.println();
+    delay(5000);                    // Delay so we don't saturate the serial output
+  }
+  else {                           // Nothing is connected in the bus 
+    Serial.println("Nothing connected");
+    delay(3000);
+  }
+}
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