add command to erase a section of flash

used by picotool as part of the write, so we'll do the same

gp2040ce_bintools/pico.py

@@ -13,6 +13,7 @@ PICO_VENDOR = 0x2e8a
 PICO_PRODUCT = 0x0003
 
 PICOBOOT_CMD_STRUCT = '<LLBBxxL'
+PICOBOOT_CMD_ERASE_SUFFIX_STRUCT = 'LL8x'
 PICOBOOT_CMD_EXCLUSIVE_ACCESS_SUFFIX_STRUCT = 'L12x'
 PICOBOOT_CMD_EXIT_XIP_SUFFIX_STRUCT = '16x'
 PICOBOOT_CMD_READ_SUFFIX_STRUCT = 'LL8x'
@@ -24,6 +25,7 @@ PICO_SRAM_END = 0x20042000
 PICO_COMMANDS = {
     'EXCLUSIVE_ACCESS': 0x1,
     'REBOOT': 0x2,
+    'ERASE': 0x3,
     'READ': 0x4,
     'EXIT_XIP': 0x6,
 }
@@ -78,6 +80,27 @@ def exclusive_access(out_end: usb.core.Endpoint, in_end: usb.core.Endpoint, is_e
     _ = in_end.read(256)
 
 
+def erase(out_end: usb.core.Endpoint, in_end: usb.core.Endpoint, location: int, size: int) -> None:
+    """Erase a section of flash memory on a Pico in BOOTSEL mode.
+
+    Args:
+        out_endpoint: the out direction USB endpoint to write to
+        in_endpoint: the in direction USB endpoint to read from
+        location: memory address of where to start erasing from
+        size: number of bytes to erase
+    """
+    # set up the data
+    pico_token = 1
+    command_size = 8
+    transfer_len = 0
+    payload = struct.pack(PICOBOOT_CMD_STRUCT + PICOBOOT_CMD_ERASE_SUFFIX_STRUCT,
+                          PICO_MAGIC, pico_token, PICO_COMMANDS['ERASE'], command_size, transfer_len,
+                          location, size)
+    logger.debug("ERASE: %s", payload)
+    out_end.write(payload)
+    _ = in_end.read(256)
+
+
 def exit_xip(out_end: usb.core.Endpoint, in_end: usb.core.Endpoint) -> None:
     """Exit XIP on a Pico in BOOTSEL.
 

tests/test_pico.py

@@ -52,6 +52,16 @@ def test_exit_xip():
     end_in.read.assert_called_once()
 
 
+def test_erase():
+    """Test that we can send a command to erase a section of memory."""
+    end_out, end_in = mock.MagicMock(), mock.MagicMock()
+    pico.erase(end_out, end_in, 0x101FE000, 8192)
+
+    payload = struct.pack('<LLBBxxLLL8x', 0x431fd10b, 1, 0x3, 8, 0, 0x101FE000, 8192)
+    end_out.write.assert_called_with(payload)
+    end_in.read.assert_called_once()
+
+
 def test_read():
     """Test that we can read a memory of a BOOTSEL board in a variety of conditions."""
     end_out, end_in = mock.MagicMock(), mock.MagicMock()