Differences
This shows you the differences between two versions of the page.
|
arduino:uPD7228_driver_library [2019/01/16 09:55] tony |
arduino:uPD7228_driver_library [2023/03/12 21:57] (current) tony |
||
|---|---|---|---|
| Line 37: | Line 37: | ||
| ===== Hardware description ===== | ===== Hardware description ===== | ||
| - | The controller consists of two μPD7228 chips, one acting as master, the second as slave. These are setup with hardwired addresses, the master is always 0x00. On the first board the slave was 0x01, on the second board it responded to 0x01 or 0x11. Each controls one half of the display. Viewed from the front of the display (with the chips not visible), the master (0x00) is on the left and controls the first 10 characters of both lines, and the slave is on the right and drives the second two rows of ten characters. | + | The controller consists of two μPD7228 chips, one acting as master, the second as slave. These are set up with hardwired addresses, the master is always 0x00. On the first board the slave was 0x01, on the second board it responded to 0x01 or 0x11. Each controls one half of the display. Viewed from the front of the display (with the chips not visible), the master (0x00) is on the left and controls the first 10 characters of both lines, and the slave is on the right and drives the second two rows of ten characters. |
| - | {{arduino:uPD7228:P1266782a.jpg?50 |uPD7228 pixel layout}}The standard chips have a 5 by 7 pixel ASCII and Japanese (Katakana) character set, with a separate 8th underscore row for a cursor. The chip's bit memory is mapped directly to individual pixels, so that each displayed character is displayed from 5 consecutive bytes of ram. In character mode the chip fills those five bytes (well, seven bits of those bytes, the 8th being for a cursor line) from the inbuilt character ROM, and decrements the address pointer by 5. Columns of pixels are numbered from the left-hand address of 49, down to the right-hand address of 0 - hence they decrement addresses when they write from left to right (there is also a right-to-left entry mode if required). Additionally there is a bit mode where you can either write a byte for each of the 50 columns, or set/reset individual bits in each column. The same memory pointer is used for both character and bit mode, so you can end up writing characters displaced from their character columns, ie written across the normal character boundaries - not very useful unless you wanted to create a super smooth scroll effect. The incomplete pixel field (gaps between character rows and columns) limit the use of the pixel addressing functions for plotting data pixels. There is potential for creating any arbitrary 5x7 character, though they'd have to be written to the display as 5x bytes of column data rather than characters. I can also envisage writing a module to create bar graphs etc. | + | {{arduino:uPD7228:P1266782a.jpg?50 |uPD7228 pixel layout}}The standard chips have a 5 by 7 pixel ASCII and Japanese (Katakana) character set, with a separate 8th underscore row for a cursor. The chip's bit memory is mapped directly to individual pixels, so that each displayed character is displayed from 5 consecutive bytes of ram. In character mode the chip fills those five bytes (well, seven bits of those bytes, the 8th being for a cursor line) from the inbuilt character ROM, and decrements the address pointer by 5. Columns of pixels are numbered from the left-hand address of 49, down to the right-hand address of 0 - hence they decrement addresses when they write from left to right (there is also a right-to-left entry mode if required). Additionally, there is a bit mode where you can either write a byte for each of the 50 columns, or set/reset individual bits in each column. The same memory pointer is used for both character and bit mode, so you can end up writing characters displaced from their character columns, ie written across the normal character boundaries - not very useful unless you wanted to create a super smooth scroll effect. The incomplete pixel field (gaps between character rows and columns) limit the use of the pixel addressing functions for plotting data pixels. There is potential for creating any arbitrary 5x7 character, though they'd have to be written to the display as 5x bytes of column data rather than characters. I can also envisage writing a module to create bar graphs etc. |
| ===== Arduino to μPD7228 wiring ===== | ===== Arduino to μPD7228 wiring ===== | ||
| Line 45: | Line 45: | ||
| I haven't tried to optimize things at all, and ended up using ten Arduino control pins! The controls used are Clock, ChipSelect, Strobe, Busy, Command/Data, Reset and 4 Data lines. | I haven't tried to optimize things at all, and ended up using ten Arduino control pins! The controls used are Clock, ChipSelect, Strobe, Busy, Command/Data, Reset and 4 Data lines. | ||
| - | The clock is a continuous 1MHz clock signal for the LCD, could be replaced with a dedicated oscillator. The reset signal has to be applied together with a data signal to tell the chips how to communicate (serial/parallel), it is used once at initialization so there may be better ways to implement reset and save using this pin. The chips are selected through data bus signals sent before chip commands/data so the chip select line could possibly be replaced with an always selected jumper. Four pins are used for the chip's 4 bit data interface, the library could be re-written to use the serial mode instead. Usage of the data Strobe and Command/Data pins can't be avoided. Finally the busy pin is polled after each write to the chips, this could be ignored and replaced by suitable timeout delays. | + | The clock is a continuous 1MHz clock signal for the LCD, could be replaced with a dedicated oscillator. The reset signal has to be applied together with a data signal to tell the chips how to communicate (serial/parallel), it is used once at initialization so there may be better ways to implement reset and save using this pin. The chips are selected through data bus signals sent before chip commands/data so the chip select line could possibly be replaced with an always selected jumper. Four pins are used for the chip's 4 bit data interface, the library could be re-written to use the serial mode instead. Usage of the data Strobe and Command/Data pins can't be avoided. Finally, the busy pin is polled after each write to the chips, this could be ignored and replaced by suitable timeout delays. |
| <HTML> | <HTML> | ||
| Line 56: | Line 56: | ||
| </HTML> | </HTML> | ||
| - | According to the datasheet, having a resistor (R1) from the reset pin to VLC5 just serves to reduce current consumption from the voltage divider supplying the LCD voltage references - if reset is held high no current flows, when low (LCD running) the Arduino acts as a current sink for the voltage divider. It could equally well be connected to ground. Imayuki's example suggest a value of 680ohm to 1.5k, I expect this has an effect upon the LCD's contrast and could be replaced with a pot, but I haven't experimented with it as 1.2k gives reasonable results. | + | According to the datasheet, having a resistor (R1) from the reset pin to VLC5 just serves to reduce current consumption from the voltage divider supplying the LCD voltage references - if reset is held high no current flows, when low (LCD running) the Arduino acts as a current sink for the voltage divider. It could equally well be connected to ground. Imayuki's example suggests a value of 680ohm to 1.5k, I expect this has an effect upon the LCD's contrast and could be replaced with a pot, but I haven't experimented with it as 1.2k gives reasonable results. |
| - | {{ arduino:uPD7228:P1266775a.jpg?270|MGCS uPD7228 LCD panel connector}}The 'MGCS' display module has a 13 pin connector with 2mm pin spacing, a plug fitting this was hand wired to a connector with 2.5mm pins suitable for standard Arduino jumper hook-up wires. I used a multimeter to trace pins back to the chips to work out their designations. The essential thing is to get the power, Vdd (+5V) and Vss (GND) right or you are likely to do some damage. Often the GND is connected to the metal mounting for the LCD strip (frame ground), and the +5V can be traced to the anode of any power LED on-board. Generally every pin has to be connected correctly before anything will be displayed - wrong connections generally result in a blank display! | + | {{ arduino:uPD7228:P1266775a.jpg?270|MGCS uPD7228 LCD panel connector}}The 'MGCS' display module has a 13 pin connector with 2mm pin spacing, a plug fitting this was hand-wired to a connector with 2.5mm pins suitable for standard Arduino jumper hook-up wires. I used a multimeter to trace pins back to the chips to work out their designations. The essential thing is to get the power, Vdd (+5V) and Vss (GND) right or you are likely to do some damage. Often the GND is connected to the metal mounting for the LCD strip (frame ground), and the +5V can be traced to the anode of any power LED on-board. Generally every pin has to be connected correctly before anything will be displayed - wrong connections generally result in a blank display! |
| \\ \\ | \\ \\ | ||
| {{ arduino:uPD7228:P1286802a.jpg?270|GEB uPD7228 LCD panel connector}}The second, 'GEB' module has the same type of 13 pin connector, but the edge connector pin assignments are transposed. So the function of pin 1 became pin 13, pin 2 became pin 12 and so forth. If the plug was symmetrical we could just rotate it 180 degrees, but it only fits in one way around, so reconnecting wires was necessary. The two edge connectors on the bottom edge of this module are just wired together and don't connect to the LCD circuit at all. | {{ arduino:uPD7228:P1286802a.jpg?270|GEB uPD7228 LCD panel connector}}The second, 'GEB' module has the same type of 13 pin connector, but the edge connector pin assignments are transposed. So the function of pin 1 became pin 13, pin 2 became pin 12 and so forth. If the plug was symmetrical we could just rotate it 180 degrees, but it only fits in one way around, so reconnecting wires was necessary. The two edge connectors on the bottom edge of this module are just wired together and don't connect to the LCD circuit at all. | ||
| Line 64: | Line 64: | ||
| There was no particular reason for choosing the Arduino control pins used here, apart from the clock needing to come from a pin that supports PWM, and avoiding D0 and D1 which I assume are otherwise occupied if I use the serial monitor for debugging. The pins used are specified when invoking the init() routine through declaring an instance of the LiquidCrystal_7228 class, eg "LiquidCrystal_7228 lcd(5, 2, 3, 4, 6, 9, 10, 11, 12, 13)" (busy, strobe, chip_select, command/data, reset, clock, d0, d1, d2, d3). | There was no particular reason for choosing the Arduino control pins used here, apart from the clock needing to come from a pin that supports PWM, and avoiding D0 and D1 which I assume are otherwise occupied if I use the serial monitor for debugging. The pins used are specified when invoking the init() routine through declaring an instance of the LiquidCrystal_7228 class, eg "LiquidCrystal_7228 lcd(5, 2, 3, 4, 6, 9, 10, 11, 12, 13)" (busy, strobe, chip_select, command/data, reset, clock, d0, d1, d2, d3). | ||
| - | ===== 7228 Library ===== | + | ===== 7228 library ===== |
| - | As mentioned earlier the library is based on a standard Arduino LiquidCrystal.cpp LCD library. My implementation of these functions is not 100% the same as how the HD44780 works. Also some functions have not been implemented at all as the μPD7228 chip has no support for them, and the size of the library was getting unreasonably large already. In fact it could probably be argued that such a library should just provide high level access to the built in functions of the hardware, and not try to emulate anything else. But my aim was to create something that could be used as a drop in replacement for the displays commonly commercially available (I may have to tweak the routines to provide more compatibility with the HD44780 further down the track). The library keeps track of the cursor in terms of a column and row address, which it translates into a hardware address when required. | + | As mentioned earlier the library is based on a standard Arduino LiquidCrystal.cpp LCD library. My implementation of these functions is not 100% the same as how the HD44780 works. Also some functions have not been implemented at all as the μPD7228 chip has no support for them, and the size of the library was getting unreasonably large already. In fact it could probably be argued that such a library should just provide high-level access to the built-in functions of the hardware, and not try to emulate anything else. But my aim was to create something that could be used as a drop-in replacement for the displays commonly commercially available (I may have to tweak the routines to provide more compatibility with the HD44780 further down the track). The library keeps track of the cursor in terms of a column and row address, which it translates into a hardware address when required. |
| The functions implemented are: | The functions implemented are: | ||
| Line 107: | Line 107: | ||
| * Draw a horizontal bar graph on either line. | * Draw a horizontal bar graph on either line. | ||
| - | *1 This differs from HD44780 in that it does not have a third parameter for character size, and no testing of displays other that 20 cols x 2 lines, has been done. | + | *1 This differs from HD44780 in that it does not have a third parameter for character size, and no testing of displays other than 20 cols x 2 lines, has been done. |
| *2 This differs from HD44780 in that it only scrolls the current line, and you can choose whether lines wrap back to the start of the display, or just insert spaces, by using the lineWrap(), noLinewrap() functions. | *2 This differs from HD44780 in that it only scrolls the current line, and you can choose whether lines wrap back to the start of the display, or just insert spaces, by using the lineWrap(), noLinewrap() functions. | ||
| Line 115: | Line 115: | ||
| *4 This differs from HD44780 in that it only scrolls the current line, and supports the wrap functions. | *4 This differs from HD44780 in that it only scrolls the current line, and supports the wrap functions. | ||
| - | *5 This differs from HD44780 where characters written beyond the visible display are written into memory and will reappear dependant upon the memory mapping. | + | *5 This differs from HD44780 where characters written beyond the visible display are written into memory and will reappear depending upon the memory mapping. |
| <HTML> | <HTML> | ||
| Line 182: | Line 182: | ||
| ]]. | ]]. | ||
| + | * [[:arduino:ks0073 driver library|KS0073 SPI LCD]], LCD display panel Arduino driver | ||
| * [[:arduino:metp0000 driver library|METP0000]], NEC µPD7225 based LCD display panel Arduino driver | * [[:arduino:metp0000 driver library|METP0000]], NEC µPD7225 based LCD display panel Arduino driver | ||
| * [[:arduino:mx300 driver library|Canon MX300]], Canon MX300/310 printer LCD display panel Arduino driver. | * [[:arduino:mx300 driver library|Canon MX300]], Canon MX300/310 printer LCD display panel Arduino driver. | ||
Page Tools
arduino/uPD7228_driver_library.1547585746.txt.gz · Last modified: 2019/01/16 09:55 by tony
Except where otherwise noted, content on this wiki is licensed under the following license: CC Attribution-Share Alike 3.0 Unported