/*
Example of multiplexed chip selects for multiple displays
The test hardware uses a 74LVC138 with Y0 connected
to a 2.25" 76x284 display, and Y1-3 to 3 1.54" 240x240
displays. It should be evident from the code how to
change this to suit your setup...
*/
#include <ST7789_t3.h> // Hardware-specific library
#define MUX_CS 0
#define MUX_A 1
#define MUX_B 2
#define GBL_RST 22
#define TFT_RST -1 // shared - do reset in sketch code
#define TFT_DC 10
#define TFT_BLKL 4 // active low backlight (240x240 displays)
#define TFT_BLKH 3 // active high backlight (76x284 display)
/*
* Use 74LVC138 decoder to provide /CS signal to one of
* 4 displays, using only 3 Teensy outputs (we could
* address up to 8).
*/
static void CSfn(int which, bool negate)
{
if (negate)
digitalWriteFast(MUX_CS,1);
else
{
digitalWriteFast(MUX_A,(which&1)!=0);
digitalWriteFast(MUX_B,(which&2)!=0);
// digitalWriteFast(MUX_C,(which&4)!=0); // use for >4 displays
digitalWriteFast(MUX_CS,0);
}
}
// Provide lambda functions to assert /CS for each display
ST7789_t3 ST7789a = ST7789_t3( [](bool negate) { CSfn(3, negate); } , TFT_DC, TFT_RST);
ST7789_t3 ST7789b = ST7789_t3( [](bool negate) { CSfn(2, negate); } , TFT_DC, TFT_RST);
ST7789_t3 ST7789c = ST7789_t3( [](bool negate) { CSfn(1, negate); } , TFT_DC, TFT_RST);
ST7789_t3 ST7789d = ST7789_t3( [](bool negate) { CSfn(0, negate); } , TFT_DC, TFT_RST);
#define SCREENS 4
ST7789_t3* screens[]{&ST7789a, &ST7789b, &ST7789c, &ST7789d}; // easier to deal with an array
uint16_t bkgnds[]{CL(24,0,0), CL(0,24,0), CL(0,0,24), CL(128,96,32)};
// Show we can address each screen individually
void identify(ST7789_t3& tft, int n, uint16_t bkgnd, int inv)
{
char buf[20];
int16_t x,y;
uint16_t w,h;
// Basic settings:
tft.setRotation(1);
tft.invertDisplay(inv);
tft.fillScreen(bkgnd);
// Show screen number in the middle:
sprintf(buf,"Screen #%d",n);
tft.setTextColor(ST77XX_WHITE);
tft.setTextSize(3);
tft.getTextBounds(buf,0,0,&x,&y,&w,&h);
tft.setCursor((tft.width() - w)/2,(tft.height() - h)/2);
tft.print(buf);
// Show screen resolution at bottom right:
sprintf(buf,"%d x %d",tft.width(), tft.height());
tft.setTextSize(1);
tft.getTextBounds(buf,0,0,&x,&y,&w,&h);
tft.setCursor(tft.width() - w - 2,tft.height() - h - 2);
tft.print(buf);
}
void setup()
{
// Initialise /CS multiplexer
#define SAFE_MUX(p,v) pinMode(p, OUTPUT); digitalWrite(p,v)
SAFE_MUX(MUX_A,0);
SAFE_MUX(MUX_B,0);
SAFE_MUX(MUX_CS,1);
// Backlights on:
pinMode(TFT_BLKL, OUTPUT);
pinMode(TFT_BLKH, OUTPUT);
digitalWriteFast(TFT_BLKL,0);
digitalWriteFast(TFT_BLKH,1);
// Reset screens:
pinMode(GBL_RST, OUTPUT);
digitalWriteFast(GBL_RST,1); delay(1);
digitalWriteFast(GBL_RST,0); delay(1);
digitalWriteFast(GBL_RST,1); delay(1);
// Initialise:
for (int i=0;i<SCREENS-1;i++)
screens[i]->init();
screens[SCREENS-1]->init(76,284); // different, non-default size
// Identify:
for (int i=0;i<SCREENS;i++)
identify(*screens[i], i, bkgnds[i], i!=3);
}
void loop()
{
}
