[ln882h] Change flashing baudrate, fix connection guide (#72)

* [ln882h] improve flash read speed by changing baudrate

* [ln882h] fix UART number in help tip

Author: lamauny

ltchiptool/soc/ln882h/flash.py

@@ -11,11 +11,12 @@
 from .util.ln882htool import LN882hTool
 
 LN882H_GUIDE = [
-    "Connect UART1 of the LN882h to the USB-TTL adapter:",
+    "Connect UART0 of the LN882h to the USB-TTL adapter:",
     [
         ("PC", "LN882h"),
-        ("RX", "TX1 (GPIOA2 / P2)"),
-        ("TX", "RX1 (GPIOA3 / P3)"),
+        ("RX", "TX0 (GPIOA2 / P2)"),
+        ("TX", "RX0 (GPIOA3 / P3)"),
+        ("GND", "BOOT (GPIOA9 / P9)"),
         ("", ""),
         ("GND", "GND"),
     ],

ltchiptool/soc/ln882h/util/ln882htool.py

@@ -169,6 +169,7 @@ def flash_read(
         chunk_size: int = 256,  # maximum supported chunk size
     ) -> Generator[bytes, None, None]:
         self.link()
+        prev_baudrate = self.s.baudrate
         if not self.ramcode:
             self.ram_boot()
 
@@ -177,6 +178,10 @@ def flash_read(
                 f"Chunk size {chunk_size} exceeds the maximum allowed (256)"
             )
 
+        self.change_baudrate(LN882H_YM_BAUDRATE)
+        self.link()
+        self.push_timeout(0.02)
+
         for start in range(offset, offset + length, chunk_size):
             count = min(start + chunk_size, offset + length) - start
             debug(f"Dumping bytes: start=0x{start:X}, count=0x{count:X}")
@@ -186,10 +191,16 @@ def flash_read(
 
             valid, data = self.ym._verify_recv_checksum(True, data)
             if verify and not valid:
+                self.change_baudrate(prev_baudrate)
+                self.pop_timeout()
                 raise RuntimeError(f"Invalid checksum")
 
             yield data
 
+        self.change_baudrate(prev_baudrate)
+        self.pop_timeout()
+        info("Flash Read Successful.")
+
     def flash_write(
         self,
         offset: int,