Friday, 24 January 2014

Repetier and I2C LCD panel

I was having yet another bash at persuading my breadboard based hardware to work with the I2C connected LCD display as mentioned in my Panelolu post.

I have been bashing my head against a wall with the Repetier firmware for months. Every time I had it use the LCD and uploaded the firmware, the whole board would hang just as it reached the initialisation of the LCD display.

I had tried with the built-in I2C library as well as several other Liquid Crystal libraries, none of which would work with Repetier once the LCD part was enabled.

I could manage to talk to the PCF8574P  I2C chip and obtain the address with the Scanner program, I could also write my own code to talk to the LCD all of which seemed to work fine, yet no matter what I did the LCD would just not play ball with Repetier.

I decided to re-read a bunch of posts about the various Liquid Crystal I2C libraries along with checking the schematics used for each of them, re-check the pin configurations in Repetier and also how it was wired up on the board.

Eventually I discovered that I had the RS and RW pins backwards in uiconfig.h for Repetier and after one last compile and upload we had success and the LCD sprang into life. (kind of begs the question how it was working with the other pieces of software though).
This is my pin configuration for the LCD in uiconfig.h

What display type do you use?
0 = No display
1 = LCD Display with 4 bit data bus
2 = LCD Display with 8 bit data bus (currently not implemented, fallback to 1)
3 = LCD Display with I2C connection, 4 bit mode
4 = Use the slower LiquiedCrystal library bundled with arduino. 
    IMPORTANT: You need to uncomment the LiquidCrystal include in Repetier.pde for it to work.
               If you have Sanguino and want to use the library, you need to have Arduino 023 or older. (13.04.2012)

// This is line 2 of the status display at startup
#define UI_VERSION_STRING2 "Orig. Mendel"

/** Number of columns per row

Typical values are 16 and 20
#define UI_COLS 16
Rows of your display. 2 or 4
#define UI_ROWS 2

/* What type of chip is used for I2C communication
0 : PCF8574 or PCF8574A or compatible chips.
1 : MCP23017
// 0x40 till 0x4e for PCF8574, 0x40 for the adafruid RGB shield, 0x40 - 0x4e for MCP23017
// For MCP 23017 define which pins should be output
// Set the output mask that is or'd over the output data. This is needed to activate
// a backlight switched over the I2C. 
// The adafruit RGB shields enables a light if the bit is not set. Bits 6-8 are used for backlight.
// For MCP which inputs are with pullup. 31 = pins 0-4 for adafruid rgb shield buttons
/* How fast should the I2C clock go. The PCF8574 work only with the lowest setting 100000.
A MCP23017 can run also with 400000 Hz */
#define UI_I2C_CLOCKSPEED 100000L
Define the pin
#if UI_DISPLAY_TYPE==3 // I2C Pin configuration
#define UI_DISPLAY_RS_PIN _BV(4)
#define UI_DISPLAY_RW_PIN _BV(5)
#define UI_DISPLAY_D0_PIN _BV(0)
#define UI_DISPLAY_D1_PIN _BV(1)
#define UI_DISPLAY_D2_PIN _BV(2)
#define UI_DISPLAY_D3_PIN _BV(3)
#define UI_DISPLAY_D4_PIN _BV(0)
#define UI_DISPLAY_D5_PIN _BV(1)
#define UI_DISPLAY_D6_PIN _BV(2)
#define UI_DISPLAY_D7_PIN _BV(3)

The _BV values are the P0-P7 pins from the PCF8574P chip - I only needed P0-P6, D0-D4 are for the low nibble, D5-D8 for the high nibble, you can connect in 8-bit mode if you have enough pins (D0-D7), or you can connect in 4-bit mode (D5-D7), you just pretend that both sets are connected to the same pins and both the low and high nibble data is transferred over these 4 pins.

As mentioned in my Firmware and Making Fumes post, I have 10 pins to play with (13 if you include MOSI, MISO and SCK) on the sanguinololu.

Now I have reduced my LCD pin requirement from 6 to 2, I have a few more to play with, which means I can use the buzzer again, and still have 3 pins spare.

Physical Pin #Pin NameSanguinololu PinArduino UseMy Use
40PA0A0/D31GP I/OSD card CS
9RSTRSTRSTReset Button
38PA2A2/D29GP I/OEncoder 1
39PA1A1/D30GP I/OEncoder 2
16PD2D10RX1Encoder C
37PA3A3/D28GP I/OBuzzer
36PA4A4/D27GP I/OFree

Whilst at a first glance, this might not seem the most logical layout, it makes more sense if you look at the way the pins are actually laid out on the sanguinololu.
I believe I have mentioned it already, but I am not interested in running any firmware that will not compile against a relatively current version of Arduino, (trying to obtain any support for issues with older versions is quite simply a pain), as such I am only interested in firmware that will compile against Arduino 1.0 or greater (I am currently using 1.0.5).

I have not compiled in the extra code for the rotary encoder or the buzzer yet, but things are looking good for using an ATmega644P rather than needing the more expensive ATmega1284P, as the compiled code is only 47,928 bytes. Previously with the Marlin firmware, after enabling the LCD code, I was beyond the 64Kb limit of the ATmega644P.

Here is a possible interface board for the panelolu.
And without the components covering the connections.
The only real difference from the schematic is that the connections for pins 9 and 11 (P4 and P6) have been swapped in order to make wiring simpler.

Wednesday, 22 January 2014

Prusa i3 Physical Build (part 3)

Progress on the build has been somewhat slow recently (almost non-existant for a couple of months).

I eventually caved in and bought a J-Head MK IV hot end from ebay for £21.99.

and an Airtripper extruder for £15.95.

I have made some progress however with the wiring and neatening up some of the cables.
 Here you can see the reworked end of the Xbox power cable and a few other wires that have been routed and had connectors applied.
I also decided that my "free" belts were too narrow (2mm), and did not really stay put when tensioned. So I bought a 10m reel of GT2 belt for £17.61 from ebay and used about 1m each for the X and Y axes (they actually fit the pulleys that came with my steppers better than the T2 belts did, so they were probably GT2 pulleys after all) the rest will be used on future 3D printers or other CNC machines - I see a DIY laser cutter in the future at some point.
I have finally wired up the PCB heated plate using some surface mount components - 2 x LEDs and a 1K resistor.
I have also started on wiring up my hall effect sensors (10 for £2.43 from ebay) for the homing switches. I drilled an extra hole in the bracket to allow for some strain relief.
Here is a shot of the hot end and a home made mount made from some aluminium angle and a small chunk of hdpe (cut from a £3.00 chopping board).
I added a fan that happened to be the right size that was lying around from some scrapped piece of kit and ran this wire to one of the 12v output connectors on the sanguinololu. As you can see I have connected the J-Head via a bowden tube using a pneumatic fitting.
Here is the other end of the ptfe bowden tube connected to the Airtripper extruder, now attached to a stepper motor and mounted on top of the frame.
 Current progress shot from the front of the unit.
I still have some more wiring to do - I need some different pins for the extruder motor as these use a different JST connector with a 2.5mm spacing, a pack of 100 pins is £4.20 +VAT from RS. I have 4 more of these motors, so I think I will buy a pack and reuse the nylon connectors that came with the motors rather than join the individual wires.

I am also waiting on sone kapton tape I bought on ebay to arrive from Hong Kong so I can finish connecting the thermistor for the PCB heated bed.

I still have 2 more hall effect sensors to connect up and position as well as positioning the 6x2mm round neodymium magnets (10 for £1.18 from ebay) to activate them.