{"id":40,"date":"2012-10-07T17:54:00","date_gmt":"2012-10-07T16:54:00","guid":{"rendered":"https:\/\/blog.hslracing.com\/3dprinters\/2012\/10\/07\/atmega1284p-marlin-and-i2c\/"},"modified":"2012-10-07T17:54:00","modified_gmt":"2012-10-07T16:54:00","slug":"marlin-and-atmega1284p-and-i2c","status":"publish","type":"post","link":"https:\/\/blog.hslracing.com\/3dprinters\/2012\/10\/marlin-and-atmega1284p-and-i2c.html","title":{"rendered":"ATmega1284P, Marlin and I2C"},"content":{"rendered":"

I bought a few items from RS<\/a> on a visit to their Hounslow branch and revived my account that had been dormant for nearly 10 years!<\/p>\n

JST 2mm pitch 6 way connectors<\/a> for running new wires to my Steppers (50 pack for \u00a33.30)
Crimp Contact Pins<\/a> for the connectors (50 pack for \u00a31.60)
ATmega1284P-PU<\/a> Microcontroller (\u00a34.55 each)
Nylon Screw Insulator<\/a> Rail bushings for my cast Prusa parts (50 pack for \u00a33.67)<\/p>\n

Not all parts were in stock at that branch, so I arranged for out of stock parts to be posted to me (one of the perks of an RS<\/a> account is that the postage is free).<\/p>\n

RS<\/a> are often not the cheapest, but they do have hard to locate parts, like the JST connectors, and I do not need to worry about building a large order to offset postage costs of places like Rapid<\/a> or Farnell<\/a>.<\/p>\n

The ATmega1284P from RS<\/a> is half the price of the cheapest one I can find anywhere else – cheapest I can find is on Ebay<\/a> for \u00a37.99 with \u00a31.20 postage.<\/p>\n

I replaced the ATmega644P chip on my breadboard with the new 1284P chip, updated the settings in Arduino<\/a> for “Mighty” and burned the bootloader and then uploaded the latest version of Marlin<\/a> that actually compiles with a current version of Arduino<\/a> (1.0 or 1.0.1) – all good so far.<\/p>\n

Dowloaded the LiquidCrystal_I2C<\/a> library and put the files in the relevant Arduino <\/a>directory, then started splicing it into Marlin<\/a>, very little to it as it happens – every file that has a reference for LiquidCrystal just needs to have an equivalent one for LiquidCrystal_I2C added.<\/p>\n

Configuration.h<\/u><\/p>\n

change
\/\/LCD and SD support (Manual definitions if not using ULTIPANEL)
#define ULTRA_LCD  \/\/general lcd support, also 16×2<\/p>\n

<\/div>\n
to<\/div>\n
\n
\/\/LCD and SD support (Manual definitions if not using ULTIPANEL)<\/div>\n
#define I2C_LCD 0x27  \/\/ I2C LCD Panel (overrides the LiquidCrystal library with LiquidCrystal_I2C) – value is I2C Address for LCD<\/div>\n
#define ULTRA_LCD  \/\/general lcd support, also 16×2<\/div>\n<\/div>\n
<\/div>\n

ultralcd.h<\/u><\/p>\n

change
#include <LiquidCrystal.h><\/p>\n

to
#ifdef I2C_LCD
  #include <LiquidCrystal_I2C.h>
#else
  #include <LiquidCrystal.h>
#endif<\/p>\n

and
extern LiquidCrystal lcd;<\/p>\n

to
#ifdef I2C_LCD
  extern LiquidCrystal_I2C lcd;
#else
  extern LiquidCrystal lcd;
#endif<\/p>\n

ultralcd.ino<\/u><\/p>\n

change
#include <LiquidCrystal.h><\/p>\n

to
#ifdef I2C_LCD
  #include <LiquidCrystal_I2C.h>
#else
  #include <LiquidCrystal.h>
#endif<\/p>\n

and
LiquidCrystal lcd(LCD_PINS_RS, LCD_PINS_ENABLE, LCD_PINS_D4, LCD_PINS_D5,LCD_PINS_D6,LCD_PINS_D7);  \/\/RS,Enable,D4,D5,D6,D7<\/p>\n

to
#ifdef I2C_LCD
  LiquidCrystal_I2C lcd(I2C_LCD, LCD_WIDTH, LCD_HEIGHT);
#else
  LiquidCrystal lcd(LCD_PINS_RS, LCD_PINS_ENABLE, LCD_PINS_D4, LCD_PINS_D5,LCD_PINS_D6,LCD_PINS_D7);  \/\/RS,Enable,D4,D5,D6,D7
#endif<\/p>\n

Then re-compile and upload to the bigger ATmega1284P chip.<\/p>\n

Everything worked fine, except that when I connect to the chip from Printrun<\/a>, the printer no longer comes online.<\/p>\n

Now this could be because I don’t actually have a connection to an I2C chip or LCD display at this moment in time, I will have to wait until I have one to prove one way or the other.<\/p>\n

I have a bunch of 8 bit I2C Expander<\/a> chips on order (10 x PCF8574 for \u00a33.71) but they seem to be lost in the post at present, looks like I will need to have the Ebay<\/a> vendor resend them.<\/p>\n

An alternative, but slightly more expensive option is an I2C LCD interface board.<\/p>\n

<\/a><\/div>\n

These can be had on Ebay<\/a> for as little as \u00a32.44 each, I can wire my own for about \u00a30.70 with the chips mentioned previously (37p for the I2C expander, 3p for the transistor, 25p for the potentiometer and a few more pennies for the pin headers and some perf board).<\/p>\n

The main benefit of using the I2C version is that only 2 pins, SCL (D16) and SDA (D17) are required, along with a 5V and GND, and these can be spliced from any existing supply pins, compared with 6 dedicated pins for running the LCD directly.<\/p>\n

In addition, any other I2C devices can be added with no extra pins being required as it is a bus based technology.<\/p>\n

A unique address for each I2C device, which can be set by choosing which of the 3 Address pins are connected to 5V on the 8 bit I2C Expander<\/a>:<\/p>\n

Address pins A0, A1 and A2 make up the last 3 bits of a 7 bit binary number, so the available range is from 0100000 (32 decimal or 0x20 hex) – 0100111 (39 decimal or 0x27 hex).<\/p>\n

Typical connectivity to an LCD panel as follows (image from Pavel Bansky’s<\/a> website):<\/p>\n

<\/a><\/div>\n
I don’t have any BC548B<\/a> NPN transistors, plus they are end of life anyway, however I do have a C945<\/a> which should be a close enough substitute, but since this is only really for adjusting brightness I will probably just connect it to either a resistor or a potentiometer and adjust manually.<\/div>\n
<\/div>\n
I also ordered some stepstick<\/a> A4983 units from Ebay<\/a>, these ones do 1\/16 microstepping and are only \u00a34.43 each, so nearly half the price of the previous ones I bought from Denmark and free shipping from China.<\/div>\n","protected":false},"excerpt":{"rendered":"

I bought a few items from RS on a visit to their Hounslow branch and revived my account that had been dormant for nearly 10 years! JST 2mm pitch 6 way connectors for running new wires to my Steppers (50 pack for \u00a33.30)Crimp Contact Pins for the connectors (50 pack for \u00a31.60)ATmega1284P-PU Microcontroller (\u00a34.55 each)Nylon Screw Insulator Rail bushings…<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[1],"tags":[],"class_list":["post-40","post","type-post","status-publish","format-standard","hentry","category-uncategorised"],"_links":{"self":[{"href":"https:\/\/blog.hslracing.com\/3dprinters\/wp-json\/wp\/v2\/posts\/40","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/blog.hslracing.com\/3dprinters\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/blog.hslracing.com\/3dprinters\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/blog.hslracing.com\/3dprinters\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/blog.hslracing.com\/3dprinters\/wp-json\/wp\/v2\/comments?post=40"}],"version-history":[{"count":0,"href":"https:\/\/blog.hslracing.com\/3dprinters\/wp-json\/wp\/v2\/posts\/40\/revisions"}],"wp:attachment":[{"href":"https:\/\/blog.hslracing.com\/3dprinters\/wp-json\/wp\/v2\/media?parent=40"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/blog.hslracing.com\/3dprinters\/wp-json\/wp\/v2\/categories?post=40"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/blog.hslracing.com\/3dprinters\/wp-json\/wp\/v2\/tags?post=40"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}