Difference between revisions of "SPI LCD"
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#REDIRECT [[LCD]] |
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[[File:SPI_LCD.jpg|thumb|300px|alt=The SPI_LCD board|The SPI_LCD board]] |
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This is the documentation page for the SPI_LCD board. |
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== Overview == |
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== Assembly instructions == |
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The board comes assembled. No assembly required. |
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=== Possible Configurations === |
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* The board could be configured with software for I2C. |
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* The seconde SPI connector can be jumpered to be the ICSP connector for the AVR CPU on the board. |
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== External resources == |
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=== Datasheets === |
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[http://www.atmel.com/Images/doc8006.pdf The datasheet of the Attiny44 processor] that is the "brains" of the board. |
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SPI connector: |
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[http://www.batsocks.co.uk/readme/isp_headers.htm We use the 6-pin header]. The pin labeled "RESET" when the connector is used as ICSP header should be labeled "slave select" when used for SPI datatransfer. |
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== Additional software == |
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=== Related projects === |
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== Pinout == |
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=== SPI === |
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[[SPI connector pinout]] |
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=== LCD === |
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{| border=1 |
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! pin !! name |
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|- |
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| 1 || VSS |
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|- |
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| 2 || VDD |
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|- |
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| 3 || VO (contrast) |
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|- |
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| 4 || RS |
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|- |
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| 5 || RW (GND) |
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|- |
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| 6 || EN |
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|- |
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| 7 || DB0 (NC) |
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|- |
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| 8 || DB1 (NC) |
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|- |
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| 9 || DB2 (NC) |
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|- |
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| 10 || DB3 (NC) |
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|- |
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| 11 || DB4 |
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|- |
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| 12 || DB5 |
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|- |
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| 13 || DB6 |
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|- |
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| 14 || DB7 |
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|- |
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| 15 || BL + (VCC) |
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|- |
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| 16 || BL - (PWM) |
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|- |
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|} |
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=== LEDs === |
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None. The board doesn't have leds. The next hardware revision might have a powerled. |
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== Power == |
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The board can be powered from 3.3V or 5V. However the LCDs that I have don't work with a VCC of 3.3V. |
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== Jumper settings == |
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There are two solder jumpers. The one between the two 6-pin SPI connectors controls the function of the SPI connector nearest the I2C connectors. |
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In the default configuration the second SPI connector is a daisy-chain connector for the SPI bus. |
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In the other configuration, the second SPI connector is the ICSP connector. |
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The second solder jumper connects "rs" and "vo" of the LCD together (and to one pin of the attiny44 controller on the board) in the default configuration. |
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In the other configuration, the pin used for SPI slave select can be used as the RS pin. This is used in the I2C configuration. |
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See [[solder jumpers]] for more information on how to change the setting. |
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== Programming == |
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To display a string on the LCD, just send over SPI the same bytes you would send to LCD, prefixed with the address of the LCD (the default address is 0x82). |
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Bytes above 0xf0 are "special". |
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0xf0 <xy> is set cursor. the <xy> byte is 3 bit line number and 5 bit position number. This addressing allows up to 8 lines of 32 characters. |
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0xf1 is clear LCD. |
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0xf2 <addr> is "set address". If you want to change the address the module reacts to. The address is stored in eeprom, and will remain this way after a powercycle. |
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0xf3 <contrast> is "set contrast". This will set the contrast to the value you specify. 0x40 is the default that works fine for the LCDs that we have. |
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0xf4 <backlight> is the "set backlight intensity" command. This will set the backlight intensity to the value specified. |
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0xf5 <byte> will send the byte as a command to the HD44780. You need this for example to use the user-defined characters. |
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0xff <byte> will send the byte to the LCD without special character processing. This allows you to send codes 0xf0 through 0xff to the LCD if required. |
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Other bytes between 0xf0 and 0xff are reserved and are currently implemented as a no-op. |
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When you send a "read" request there are two different commands: |
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0x01: "Identify". The board will respond with "spi_lcd 1.2". The version number is subject to change of course. The string is zero-terminated. |
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0x02: "serial number". The board will respond with the 32-bit serial number. (After that the remaining bytes of the eeprom will be sent). |
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== The software == |
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The attiny44 runs the software from here: http://www.bitwizard.nl/tw_spi/ |
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The "tw_spi_general" package includes the code for the spi_lcd board in the lcd subdirectory. |
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A sample project which operates as a master is located here: |
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http://www.bitwizard.nl/spi_atmega/ |
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== Default operation == |
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By default the board boots up and shows "tiny-spi-LCD <version>" and the address on line 2. |
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The opening screen clears automatically when you first send any data. |
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Future versions of the software may allow changing the opening text through the SPI interface. |
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== Physical size == |
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The board is 50x20mm. The mounting holes are 3mm from the edges. So the distances between the holes are 47x17mm. |
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== Future hardware enhancements == |
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* power led. |
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== Future software enhancements == |
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* Allow customization of the opening text. |
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* Allow different sizes of LCDs. |
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== Changelog == |
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=== 1.2 === |
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* Initial public release |
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Latest revision as of 15:51, 21 May 2012
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