Picaxe as a Slave device

shah_siddiquee · May 15, 2016

hi, i am trying to communicate picaxe with arduino using i2c, I want to use picaxe as a slave and arduino as a Master. i got an example of writing data to slave picaxe, but i am struggling to read data from it. There are a very few information about using picaxe as a slave. and few parts for it (X1 and X2) as well. Can anyone please help me to read data from picaxe to arduino. i mean what should be the code for picaxe .

hippy · May 15, 2016

Untested, but the following should emulate a byte addressed Eeprom with 8-bit Device Address $A0 -

Code:

HI2cSetup I2CSLAVE, $A0

Put 0, "H"
Put 1, "e"
Put 2, "l"
Put 3, "l"
Put 4, "o"

Do
  Pause 1000
Loop

Reading location 0 onwards from Device Address $A0 (8-bit) or $50 (7-bit) should return the values which have previously been put to Scratchpad by the PICAXE program.

shah_siddiquee · May 16, 2016

hippy said:
Untested, but the following should emulate a byte addressed Eeprom with 8-bit Device Address $A0 -

Code:

HI2cSetup I2CSLAVE, $A0 Put 0, "H" Put 1, "e" Put 2, "l" Put 3, "l" Put 4, "o" Do Pause 1000 Loop

Reading location 0 onwards from Device Address $A0 (8-bit) or $50 (7-bit) should return the values which have previously been put to Scratchpad by the PICAXE program.

Thanks Hippy, but how arduino can read data from picaxe scratchpad. please don't mind for my ignorance about that. i am a beginner.

hippy · May 16, 2016

The Arduino should be configured and read the PICAXE just as it would for an I2C Eeprom with 256 bytes of byte memory.

I personally have no idea what the specific code would be. It is probably better to ask on an Ardunio forum though some PICAXE users may know the code to use.

What the PICAXE puts into or gets from scratchpad is what the I2C master can read or write.

oracacle · May 16, 2016

the picaxe, while in slave mode should behave as any i2c device, once the picaxe has its address established as per hippys' example its down to the Arduino to do the rest. Arduino has a forum so you maybe better off asking over there

Edit: Ninja'd by hippy

shah_siddiquee · May 16, 2016

I post that on arduino forum, its been 2 day and only one reply and its says to ask on picaxe forum. thanks anyway for your reply.

lbenson · May 16, 2016

Don't ask on arduino forum about picaxe--ask about reading/writing an I2C Eeprom with 256 bytes, addressed at $50 (7-bit), which is what the picaxe looks like when an i2c slave.

Simmicht · May 21, 2016

I too, am trying to use my ever-loving 28X1 as a I2C slave for my Arduino project.
So far no luck, but I will do my best to get this to happen.

Basically I have a ESP8266 Arduino core and I want to read a MQ-7 Carbon Monoxide sensor. The ESP8266 has only one analogue input and it has a max of 1V.
So I will try to use a 28X1 to read the analogue values and present them to the ESP8266 when it wants them. There are already HTU21 (Temp and humidty) BMP180 for atmospheric pressure and BH1750 for light values.

Connections be like :
Picaxe28X1 pin 14 SCL to Arduino pin A5 SCL
Picaxe28X1 pin 15 SDA to Arduino pin A4 SDA
4K7 pullups to 5V on both line

The Arduino code be like:
#include <Wire.h>

voidsetup(){
Wire.begin();// join i2c bus (address optional for master)
Serial.begin(9600);// start serial for output
}

voidloop(){
Wire.requestFrom(8,6);// request 6 bytes from slave device #8

while(Wire.available()){// slave may send less than requested
char c = Wire.read();// receive a byte as character
Serial.print(c);// print the character
}

delay(500);
}

Terry

lbenson · May 21, 2016

I'm not entirely certain what this code means, and I don't know the arduino code, but I don't see anywhere that the slave picaxe address of $50 is mentioned, and the comment "slave may send less than requested" is not applicable to the process of reading a fixed number of bytes from an i2c 128-byte eeprom (what a slave picaxe looks like).

Simmicht · May 21, 2016

the $50 is %1010 000 the 7 bit form which is the right I2C address when the slave is set to %10100000 .
The arduino will shift left and add bit0 to be read/write.

28X1 code

Code:

#picaxe 28X1
#terminal 9600
#no_data
#no_table


setfreq EM8


pause 2000
Sertxd("START",cr,lf)
'do
'pause 2000
'Sertxd("START",cr,lf)
'loop


init: hi2csetup i2cslave, %10100000




Put 0, "H"
Put 1, "e"
Put 2, "l"
Put 3, "l"
Put 4, "o"
Put 5, "W"
Put 6, "O"
Put 7, "R"
Put 8, "L"
Put 9, "D"
Put 10, "1"
Put 11, "2"
Put 12, "3"
Put 13, "4"
Put 14, "5"
Put 15, "6"


Do
  Pause 1000
  
LOOP

Arduino code

Code:

#include <Wire.h>
 
void setup(){
  Serial.begin(115200);


  delay(1000);
  Serial.println(F("I2C TEST Starting"));


Wire.begin();


Serial.println("oK");
}






 
void loop(){
Serial.print("\n>");


//Wire.beginTransmission(80); // transmit to device #80
//Wire.write("A");           // queue one byte
//Wire.endTransmission();    // send by transmitting


  Wire.requestFrom(0x50, 16,false);    // request 16 bytes from slave device #8
  delay(400);
  while (Wire.available()) { // slave may send less than requested
    char c = Wire.read(); // receive a byte as character
    if (c<32) Serial.print(".");
    else      Serial.print(c);         // print the character
  }




delay(5000);
 
}

and the output

Code:

>HelloWORLD123456
>................
>................
>................
>................
>................
>................
>................
>HelloWORLD123456
>................
>................
>................
>................
>................
>................
>................
>HelloWORLD123456
>................
>................

Seems like the read is just looping through the 28X1 memory.
How can I tell it where to read?

Terry

inglewoodpete · May 21, 2016

Simmicht said:
and the output

Code:

>HelloWORLD123456 >................ >................ >................ >................ >................ >................ >................ >HelloWORLD123456 >................ >................ >................ >................ >................ >................ >................ >HelloWORLD123456 >................ >................

Seems like the read is just looping through the 28X1 memory.
How can I tell it where to read?

Terry

It looks like the 28x1 slave is working perfectly. Your question needs to be addressed to an Arduino forum.

When reading from an i2c slave, you need 3 parameters: (1) The slave device's address (2) The start point in the slave's memory map (3) The number of bytes to be read. Of course, at some point the master must know how big a memory the slave has - and therefore use an 8-bit (max 256 bytes) or 16-bit address (max 65536 bytes) as the start point for pointing into the slave's memory map.

Simmicht · May 21, 2016

ok i found the way.

the Arduino code needed a write to the address the subsequent reads are to be from.

Arduino code

Code:

#include <Wire.h>
void setup(){
  Serial.begin(115200);


  delay(1000);
  Serial.println(F("I2C TEST Starting"));


Wire.begin();


Serial.println("oK");
 
}


void loop(){
 


Serial.print("\n>");


Wire.beginTransmission(0x50); // transmit to device #80
Wire.write(0);           // queue one byte
Wire.endTransmission();    // send by transmitting


  Wire.requestFrom(0x50, 16);    // request 16 bytes from slave device #8
  delay(400);
  while (Wire.available()) { // slave may send less than requested
    char c = Wire.read(); // receive a byte as character
    if (c<32) Serial.print(".");
    else      Serial.print(c);         // print the character
  }




delay(5000);
 
}

Simmicht · May 21, 2016

A working example, usinf Arduino to get a WORD from 28X1 as I2C slave.

Arduino

Code:

#include <Wire.h>


 
void setup(){
  Serial.begin(115200);


  delay(1000);
  Serial.println(F("I2C TEST Starting"));


Wire.begin();


Serial.println("oK");
}
 
void loop(){
Serial.print("\n>");


Wire.beginTransmission(0x50); // transmit to device #80
Wire.write(100);           // queue one byte from Picaxe SP=100
Wire.endTransmission();    // send by transmitting


Wire.requestFrom(0x50, 2);    // request 16 bytes from slave device #8
delay(400);


uint16_t t = Wire.read();
t  += Wire.read() *256 ;
 //t  = t2*256 + t1;
Serial.print(t);     // print the integer


delay(5000);
 
}

28X1

Code:

#picaxe 28X1
#terminal 9600
#no_data
#no_table


setfreq EM8


pause 2000
Sertxd("START",cr,lf)
'do
'pause 2000
'Sertxd("START",cr,lf)
'loop


init: hi2csetup i2cslave, %10100000




Do
  Pause 2000
  inc w2
  put 100, WORD w2
  Sertxd(#w2,cr,lf)
  
LOOP

Output

Code:

>512
>518
>523
>529
>534
>540

stevercarter · Sep 6, 2016

I wish to use say a 20m as master and serial connect say 4 20m as slave units
I want the slave units to replicate the master outputs

lbenson · Sep 7, 2016

stevercarter said:
.. 20m as slave units

Only "X" devices can be i2c slaves, e.g., 20X2--not "M" picaxes.

hippy · Sep 7, 2016

I think the question has previously passed through Technical Support and is a more generic question on slaving PICAXE devices than using PICAXE as an I2C slave device.

I have duplicated the question in the Active Forum -

http://www.picaxeforum.co.uk/showthread.php?29233-Slave-outputs-from-master

Picaxe as a Slave device

shah_siddiquee

Member

hippy

Ex-Staff (retired)

shah_siddiquee

Member

hippy

Ex-Staff (retired)

oracacle

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shah_siddiquee

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lbenson

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Simmicht

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lbenson

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Simmicht

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inglewoodpete

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Simmicht

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Simmicht

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stevercarter

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lbenson

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hippy

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