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last updated: 2023-07-24
A very sad matrix display was waiting for 2 years in a box to transform finally in an analog clock.
The display has 64x64 RGB LEDs with a 3 mm pitch and can be purchased among others from adafruit: https://www.adafruit.com/product/4732.
We need an adapter. I used the active adapter PCB to support up to 3 panel chains from Henner Zeller (hzeller): https://github.com/hzeller/rpi-rgb-led-matrix/tree/master/adapter/active-3.
This works with every Raspberry Pi version.
The same Henner Zeller wrote a cool library to use these displays with a Raspi. Everything is explained here: https://github.com/hzeller/rpi-rgb-led-matrix. Clone the repo:
git clone https://github.com/hzeller/rpi-rgb-led-matrix.git
or download the zip file and extract it.
In the folder examples-api-use you find examples in C++ to test the displays.
As I use a Raspi4, I need to set the flag --led-slowdown-gpio=5 to avoid flicker on the display.
Unfortunately there was no analog clock in the examples, so I had to take a closer look at the library and write my own code.
First we need to add some things to the Makefile. We add the program name to the third (Objects=...) and fourth line (BINARIES=...) and add a line after the 33 line (pixel-mover : pixel-mover.o).
OBJECTS=demo-main.o minimal-example.o ... pixel-mover.o piaclock.o
BINARIES=demo minimal-example ... pixel-mover piaclock
...
pixel-mover : pixel-mover.o
piaclock : piaclock
Alternatively you use Makefile from my repo.
Now save the code below as piaclock.cc to the examples-api-use folder.
with make we create the binary file and are then able to run the program:
cd rpi-rgb-led-matrix/examples-api-use
sudo make
sudo ./piaclock --led-slowdown-gpio=5
// -*- mode: c++; c-basic-offset: 2; indent-tabs-mode: nil; -*-
// weigu.lu
// Small example of an analog clock on a 64x64 matrix.
// For more examples, look at demo-main.cc
//
// This code is public domain
// (but note, that the led-matrix library this depends on is GPL v2)
#include "led-matrix.h"
#include "graphics.h"
#include <signal.h>
#include <time.h>
#include <math.h>
using namespace rgb_matrix;
volatile bool interrupt_received = false;
static void InterruptHandler(int signo) {
interrupt_received = true;
}
int main(int argc, char *argv[]) {
rgb_matrix::Font font;
RGBMatrix::Options defaults;
defaults.hardware_mapping = "regular"; // or e.g. "adafruit-hat"
defaults.rows = 64; //64x64 matrix
defaults.cols = 64;
defaults.chain_length = 1;
defaults.parallel = 1;
Canvas *canvas = RGBMatrix::CreateFromFlags(&argc, &argv, &defaults);
if (canvas == NULL)
return 1;
signal(SIGTERM, InterruptHandler);
signal(SIGINT, InterruptHandler);
const int x_center = 32;
const int y_center = 32;
// set the colors here
Color sec_color(255, 255, 255);
Color text_color(255, 50, 50);
Color min_color(50, 255, 50);
Color hour_color(50, 50, 255);
Color bg_color(0, 0, 0);
const int sec_hand_length = 25;
const int min_hand_length = 23;
const int hour_hand_length = 17;
float dot_x_sec = 0, dot_x_min = 0, dot_x_hour = 0;
float dot_y_sec = 0, dot_y_min = 0, dot_y_hour = 0;
float angle = 0;
const char *bdf_font_file = "../fonts/4x6.bdf";
font.LoadFont(bdf_font_file);
int text_xy_arr[12][2] = {
{45,10}, // 1
{55,21}, // 2
{59,35}, // 3
{55,49}, // 4
{45,60}, // 5
{31,64}, // 6
{16,60}, // 7
{6,49}, // 8
{3,35}, // 9
{2,21}, // 10
{12,10}, // 11
{29,6} // 12
};
struct tm tm;
time_t now = time(0); // get time
localtime_r(&now, &tm);
int old_sec = tm.tm_sec;
int old_min = tm.tm_min;
// draw everything for the first time
for (int hour=1; hour<13; hour++) { // draw the 12 hour numbers
rgb_matrix::DrawText(canvas,font,
text_xy_arr[hour-1][0], text_xy_arr[hour-1][1], // x,y
text_color, NULL, std::to_string(hour).c_str(),0);
}
angle = tm.tm_sec*6 - 90;
dot_x_sec = cos(angle/360 * 2 * M_PI) * sec_hand_length + 32;
dot_y_sec = sin(angle/360 * 2 * M_PI) * sec_hand_length + 32;
rgb_matrix::DrawCircle(canvas,dot_x_sec,dot_y_sec,1,sec_color);
angle = tm.tm_min*6 - 90;
dot_x_min = cos(angle/360 * 2 * M_PI) * min_hand_length + 32;
dot_y_min = sin(angle/360 * 2 * M_PI) * min_hand_length + 32;
rgb_matrix::DrawLine(canvas,x_center,y_center,dot_x_min,dot_y_min,min_color);
angle = (tm.tm_hour+(tm.tm_min/60.0))*5*6 - 90;
dot_x_hour = cos(angle/360 * 2 * M_PI) * hour_hand_length + 32;
dot_y_hour = sin(angle/360 * 2 * M_PI) * hour_hand_length + 32;
rgb_matrix::DrawLine(canvas,x_center,y_center,dot_x_hour,dot_y_hour,hour_color);
while (!interrupt_received) {
now = time(0); // get time
localtime_r(&now, &tm);
if (tm.tm_sec != old_sec) {
old_sec = tm.tm_sec;
// delete old second hand
rgb_matrix::DrawCircle(canvas,dot_x_sec,dot_y_sec,1,bg_color);
// draw new second hand
angle = tm.tm_sec*6 - 90;
dot_x_sec = cos(angle/360 * 2 * M_PI) * sec_hand_length + 32;
dot_y_sec = sin(angle/360 * 2 * M_PI) * sec_hand_length + 32;
rgb_matrix::DrawCircle(canvas,dot_x_sec,dot_y_sec,1,sec_color);
}
if (tm.tm_min != old_min) {
old_min = tm.tm_min;
// delete old min and hour hands
rgb_matrix::DrawLine(canvas,x_center,y_center,dot_x_min,dot_y_min,bg_color);
rgb_matrix::DrawLine(canvas,x_center,y_center,dot_x_hour,dot_y_hour,bg_color);
// draw new min and hour hands
angle = tm.tm_min*6 - 90;
dot_x_min = cos(angle/360 * 2 * M_PI) * min_hand_length + 32;
dot_y_min = sin(angle/360 * 2 * M_PI) * min_hand_length + 32;
rgb_matrix::DrawLine(canvas,x_center,y_center,dot_x_min,dot_y_min,min_color);
angle = (tm.tm_hour+(tm.tm_min/60.0))*5*6 - 90;
dot_x_hour = cos(angle/360 * 2 * M_PI) * hour_hand_length + 32;
dot_y_hour = sin(angle/360 * 2 * M_PI) * hour_hand_length + 32;
rgb_matrix::DrawLine(canvas,x_center,y_center,dot_x_hour,dot_y_hour,hour_color);
}
}
// Animation finished. Shut down the RGB matrix.
canvas->Clear();
delete canvas;
return 0;
}