1.8" TFT Displays
The first board we saw like this was from Adafruit a well-known Maker product design and manufacturer. Then we found a Chinese "clone" from ebay which uses the same display module as the Adafruit board. Originally the Chinese "clone" board was half the price of the Adafruit board. We bought one of the Chinese clones and got Hello World running in just a few minutes.
Then we ran the graphics example from the Adafruit library (sorry abou the blurry picture).
Generically, this is a QVGA (Quarter VGA) display. VGA is 640x480. QVGA is 160x128 (a little more than a quarter in the shorter dimension, but close enough).
- Arduino System Ready (Implies 5V operation and Arduino libraries are "out there")
- Embedded LCD controller ST7735R
- 128 x 160 Color
- SPI Bus interface
- 5V/3.3V TTL logic Compatible, can be used in 5V/3.3V IO Arduino system directly
- Build in TF Card interface socket
- Can be used in MCUs, ARMs, CPLD, FPGA, DSP platforms
A Simple Request
Here's a request to manufacturers.
- Please think about how your part can be mounted outside of the breadboard.
- Then, think about how it will be cabled up and how you can do this the best way for your part to be used.
There many hardware variants of this board available on ebay now. Unfortunately, they seem to be overtaking the board that I selected in sheer numbers. All of these variants are based on the ST7735 chip and all have the same screen resolution. The differences between the boards are:
- Supply voltage level
- Tab color
Connector pins variants
The connector variations and the supply voltage levels are linked so they are considered here together.
Separate Connector version
This version lacks any unique marking to distinguish it from other versions except that there are very few other parts on the card.
This is a 3.3V only option which doesn't work with the stock 5V Arduino. The fact that the board uses 3.3 V power is buried way down in the technical details. The price is better since it doesn't need to have the 5V regulator and 5V/3.3V level shifters that the other boards do, but it can't be connected to a "stock" Arduino. Another characteristic of this part is that the SPI connections for the display are at one end of the card and the SD card pads are at the other end of the card.
"HY-1.8 SPI" version
This variant is clearly marked with "HY-1.8 SPI".
All of these have limited technical details on their ebay sites. A picture of the rear of the display shows what looks like a Voltage regulator but seems to be missing the level translation parts that most other displays have.
The board has a 16-pin connector. The connector pinout has three unused pins and unlike the other boards it looks like the display part uses the I2C bus (the others use the SPI bus). Generally, the I2C bus is slower than the SPI bus. It looks like the part still uses the SPI pins for the MicroUSB card so it's sort of the worse of both worlds.
There is a note which says:
Note: 1. JP1: 3.3V / 5V Power Converter. 2. If you use 3.3V, please short JP1. If you use 5V, you must open JP1, or LCD will be broken.
Here's a schematic of how one person hooked up the HY-1.8 SPI display. From this schematic it looks like although the pins are marked as SDA and SCLK are actually SPI pins. The 4050N parts are used as level translators taking the +5V of the Arduino and converting it to the 3.3V of the display's SPI bus.
Here's another page where the person appears to have hooked up the part as an I2C bus. It's in Russian so I am only drawing my conclusions based on the pictures. The only problem is that they proceeded to define the pins as if they were SPI pins. If you do it this way, you'd end up with the driver selecting [SPI] which is the slowest of all possibilities.
#define cs 3 #define sclk 4 #define mosi 5 #define dc 6 #define rst 7
The site did have a useful mechanical drawing which looks like it was copied from one of the ebay sites:
This is a third variant on the theme. This board has two connectors and orients the MicroSD card out the side. The features list states:
- 100% Brand New
- 1.8" Serial Port SPI TFT LCD Display Module
- Size: 1.8 inch
- Dot Matrix: 128*160
- Module Size: 54mm(length)*35mm(width)
- Display Area Size: 37mm(length)*32mm(width)
- Input Voltage: 5V/3.3V
- Pin Definition: 1-RST 2-CE 3-D/C 4-DIN 5-CLK 6-UCC 7-BL 8-GND
- It has PCB backplane with power IC, SD card socket
- It need 4 IO port at least to drive.
- The module port is compatible with 1602 LCD and Nokia 5110/3310 LCD Display port.
Only the 8-pin connector is populated in the picture.
This is the Adafruit version of the board.
On one level this is the best of breed of the boards. It's a US manufacturer and the design is solid and dependable. It is set up to use the SPI bus and can be wired to the Arduino Hardware SPI pins for maximum performance.
- Adafruit display = $20 plus shipping.
- The Adafruit display doesn't have as good a mounting as the Chinese "clone".
- The Adafruit board looks "cooler" with rounded corners but this comes at the heavy cost of mounting holes which look too close to the connector to get a screw/nut in there.
Adafruit says that 2mm screws work but that's much less common than the 4-40 screws which the Chinese "clone" boards support.
- AdaFruit board features:
- 1.8" diagonal LCD TFT display
- 128x160 resolution, 18-bit (262,144) color
- ST7735R (datasheet) controller with built in pixel-addressable video RAM buffer
- 4 or 5 wire SPI digital interface
- Built-in microSD slot - uses 2 more digital lines
- 5V compatible! Use with 3.3V or 5V logic
- Onboard 3.3V @ 150mA LDO regulator
- 2 white LED backlight, transistor connected so you can PWM dim the backlight
- 1x10 header for easy breadboarding
- 4 x 0.9"/2mm mounting holes in corners
- Overall dimensions: 1.35" x 2.2" x 0.25" (34mm x 56mm x 6.5mm)
- I haven't tried to mount an Adafruit display, that's just my observation from the pictures.
- Adafruit also has a new shield with TFT LCD plus 5 pos switches which may be better for some uses.
- The Adafruit board does put the connector on the correct side of the board for practical use.
- Pins that go straight down perpendicular to the board end up creating a mechanical limit below the board.
- AdaFruit board features:
This is the version of the card described in this page.
- The display costs under $15 shipped from China.
- It came very quickly and was well packaged.
- The display library on the ebay site for the part looks a lot like the Adafruit library.
- The Chinese "clone" doesn't put the connector on the right side of the card.
- If you mount the display so that the panel is flush with a front panel, or even behind the front panel, the connector will stand up too tall.
- The connector should be rear mounted.
- Ideally, rear mounted and facing up would be even better for mounting since the mating wiring would then be parallel and on the back. This orientation would not be as good for breadboarding, though.
- Front mounting of the connector is even less useful for breadboarding since it forces part of the breadboard to be covered or the display to be oriented so that wiring hides the screen.
|1||GND : Power Ground|
|2||SD_CS : Chipselect for TF Card, active low|
|3||LCD_CS : Chipselect for LCD, active low|
|4||SCLK : SPI Clock|
|5||MOSI : SPI Master out Slave in|
|6||MISO : SPI Masterin Slave out|
|7||RS : Command/Data Selection|
|8||RESET : LCD controller reset, active low|
|9||BKL : LCD back light, active low|
|10||VCC : 5V power input|
These parts have various color tabs (screen protectors stickers) which have slightly different driver requirements. The Adafruit driver takes this into account by using different defines for the different tab colors. The caution here is that this is hardware dependent.