Add partial update support

drivers/uc8151/uc8151.cpp

@@ -183,7 +183,7 @@ namespace pimoroni {
     gpio_put(DC, 0); // command mode
     spi_write_blocking(spi, &reg, 1);
 
-    if(data) {
+    if(len > 0) {
       gpio_put(DC, 1); // data mode
       spi_write_blocking(spi, (const uint8_t*)data, len);
     }
@@ -191,6 +191,13 @@ namespace pimoroni {
     gpio_put(CS, 1);
   }
 
+  void UC8151::data(size_t len, const uint8_t *data) {
+    gpio_put(CS, 0);
+    gpio_put(DC, 1); // data mode
+    spi_write_blocking(spi, (const uint8_t*)data, len);
+    gpio_put(CS, 1);
+  }
+
   void UC8151::command(uint8_t reg, std::initializer_list<uint8_t> values) {
     command(reg, values.size(), (uint8_t *)values.begin());
   }
@@ -210,6 +217,49 @@ namespace pimoroni {
     *p |= b; // set bit value
   }
 
+  void UC8151::partial_update(int x, int y, int w, int h, bool blocking) {
+    // y is given in columns ("banks"), which are groups of 8 horiontal pixels
+    // x is given in pixels
+
+    int cols = h / 8;
+    int y1 = y / 8;
+    //int y2 = y1 + cols;
+
+    int rows = w;
+    int x1 = x;
+    //int x2 = x + rows;
+
+    uint8_t partial_window[7] = {
+      (uint8_t)(y),
+      (uint8_t)(y + h - 1),
+      (uint8_t)(x >> 8),
+      (uint8_t)(x & 0xff),
+      (uint8_t)((x + w - 1) >> 8),
+      (uint8_t)((x + w - 1) & 0xff),
+      0b00000001  // PT_SCAN
+    };
+    command(PON); // turn on
+    command(PTIN); // enable partial mode
+    command(PTL, sizeof(partial_window), partial_window);
+
+    command(DTM2);
+    for (auto dx = 0; dx < rows; dx++) {
+      int sx = dx + x1;
+      int sy = y1;
+      data(cols, &frame_buffer[sy + (sx * (height / 8))]);
+    }
+    command(DSP); // data stop
+
+    command(DRF); // start display refresh
+
+    if(blocking) {
+      busy_wait();
+
+      command(POF); // turn off
+    }
+    command(PTOU); // disable partial mode
+  }
+
   void UC8151::update(bool blocking) {
     command(PON); // turn on
 

drivers/uc8151/uc8151.hpp

@@ -167,8 +167,11 @@ namespace pimoroni {
     void reset();
 
     void command(uint8_t reg, size_t len, const uint8_t *data);
-    void command(uint8_t reg, std::initializer_list<uint8_t> values = {});
+    void command(uint8_t reg, std::initializer_list<uint8_t> values);
+    void command(uint8_t reg) {command(reg, 0, nullptr);};
+    void data(size_t len, const uint8_t *data);
     void update(bool blocking = true);
+    void partial_update(int x, int y, int w, int h, bool blocking = true);
     void off();
 
     void pixel(int x, int y, int v);

libraries/badger2040/badger2040.cpp

@@ -15,7 +15,7 @@ namespace pimoroni {
     // set clock speed to 12MHz to reduce the maximum current draw on the
     // battery. when updating a small, monochrome, display only every few
     // seconds or so then you don't need much processing power anyway...
-    set_sys_clock_khz(48000, true);
+    //set_sys_clock_khz(48000, true);
 
     gpio_set_function(ENABLE_3V3, GPIO_FUNC_SIO);
     gpio_set_dir(ENABLE_3V3, GPIO_OUT);
@@ -166,6 +166,26 @@ namespace pimoroni {
     _button_states |= gpio_get_all() & mask;
   }
 
+  void Badger2040::partial_update(int x, int y, int w, int h) {
+    // wait for display to not be busy
+    while(uc8151.is_busy()) {
+      tight_loop_contents();
+    }
+
+    uc8151.partial_update(x, y, w, h, true);
+
+    _button_states = 0;
+
+    // wait for display to not be busy but sample buttons in case they are
+    // pressed during this time
+    while(uc8151.is_busy()) {
+      update_button_states();
+      tight_loop_contents();
+    }
+
+    uc8151.off();
+  }
+
   void Badger2040::update() {
     // wait for display to not be busy
     while(uc8151.is_busy()) {

libraries/badger2040/badger2040.hpp

@@ -22,6 +22,7 @@ namespace pimoroni {
     Badger2040();
     void init();
     void update();
+    void partial_update(int x, int y, int w, int h);
     void halt();
     void sleep();