Merge pull request #420 from newtonick/larger-spidev-buffer

Update ST7789 to support writing to larger SPIDEV buffer

docs/manual_installation.md

@@ -215,6 +215,13 @@ workon seedsigner-env
 pwd
 ```
 
+### Optional: increase spidev buffer size
+This allows `ST7789.py` to update the LCD without performing multiple write operations because the default buffer size is 4096 bytes. The default can be changed via the  `/boot/cmdline.txt` file. You will need to add `spidev.bufsiz=131072` to the end of this single lined file command.
+
+Example `cmdline.txt` contents:
+```
+console=serial0,115200 console=tty1 root=PARTUUID=2fa4ba7e-02 rootfstype=ext4 elevator=deadline fsck.repair=yes rootwait modules-load=dwc2,g_ether spidev.bufsiz=131072
+```
 
 ### Configure `systemd` to run SeedSigner at boot:
 

src/seedsigner/gui/screens/scan_screens.py

@@ -44,7 +44,7 @@ class ScanScreen(BaseScreen):
     decoder: DecodeQR = None
     instructions_text: str = "< back  |  Scan a QR code"
     resolution: tuple[int,int] = (480, 480)
-    framerate: int = 5  # TODO: alternate optimization for Pi Zero 2W?
+    framerate: int = 6  # TODO: alternate optimization for Pi Zero 2W?
     render_rect: tuple[int,int,int,int] = None
 
 

src/seedsigner/hardware/ST7789.py

@@ -159,13 +159,11 @@ def ShowImage(self,Image,Xstart,Ystart):
         pix = arr.tobytes()
         self.SetWindows ( 0, 0, self.width, self.height)
         GPIO.output(self._dc,GPIO.HIGH)
-        for i in range(0,len(pix),4096):
-            self._spi.writebytes(pix[i:i+4096])		
+        self._spi.writebytes2(pix)	
 
     def clear(self):
         """Clear contents of image buffer"""
         _buffer = [0xff]*(self.width * self.height * 2)
         self.SetWindows ( 0, 0, self.width, self.height)
         GPIO.output(self._dc,GPIO.HIGH)
-        for i in range(0,len(_buffer),4096):
-            self._spi.writebytes(_buffer[i:i+4096])		
+        self._spi.writebytes2(_buffer)