This module contains routines for sending commands to, reading from, and writing to the ESP32.

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Read bytes from ESP to paged memory.

Input	A: _file descriptor
	BC: number of bytes to read
	DE: destination address
	H: destination page
Output	A: result
	BC: number of bytes read
	DE: next address after read
	H: destination page
	L: file descriptor

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Review/update following

Sends a byte to to the ESP2.

Input	A: Byte to send

Send bytes from main memory to ESP32.

Input	DE: Starting address
	BC: Number of bytes to write
Output	BC: Number of bytes written
Clobbered	A,DE

Send string pointed to by string descriptor.

Input	HL: String descriptor address
Clobbered	AF',BC',DE',HL'

Send string to ESP32.

Input	DE: String address
	BC: String length
Output	BC: Number of bytes written
*Clobbered	A,DE,HL