Libraries
Class RegisterTarget
extends Object
An I2C target backed by a native register array.
Controller writes start with a one- or two-byte, big-endian register address. Any following bytes update consecutive registers. A write containing only the address selects the first register for a subsequent controller read. A write containing data leaves the selected register immediately after the last byte written. Controller reads are answered directly from native memory without waiting for a Toit task, and advance the selected register by the number of bytes actually read. Controller accesses wrap at the end of the register array.
The native array is initialized to zero. Toit code can access it with indexing, read, and write while the target is active. Individual byte accesses are atomic, but multi-byte accesses are not snapshots of a controller transaction. Coordinate the two sides if multi-byte values must be observed consistently.
Register targets require an I2C peripheral with address-match clock stretching and are not supported on the original ESP32.
Class summary
Constructors
constructor --sda/int --scl/int --address/int --address-bit-size/int=7 --register-count/int=256 --register-address-byte-size/int=1 --receive-buffer-size/int=DEFAULT-TARGET-BUFFER-SIZE --pull-up/bool=false --broadcast/bool=false
Constructs a register-backed I2C target on the sda and scl GPIOs.
register-count is the number of native register bytes. The register-address-byte-size is the number of address bytes in the controller protocol and must be 1 or 2. A one-byte address can select at most 256 registers; a two-byte address can select at most 65,536.
receive-buffer-size is the largest complete controller write transaction that can update the registers. Writes exceeding it are discarded.
Methods
Closes the target and releases its pins and native register array.
Number of controller write transactions discarded due to overflow.
Returns the byte stored at index.
Stores value at index and returns it.
Whether this object is equal to the other.
Inheritance
Classes overwrite this operator to get an equality specific to their needs. Equality operators often compare the type and field contents. For example:
class Pin:
number/int
constructor .number:
operator == other:
if other is not Pin: return false
return number == other.number
A class doesn't have to follow the above format, but it must keep the operator in sync with any
hash-code method. That is, if a class has a hash-code member, then the equality and hash-code must agree. If two instances are equal (a == b), then their hash codes must also be equal (a.hash-code == b.hash-code).Stringifies this object.
Inheritance
Objects that need a human-friendly string representation should overwrite this method. The default string is based on the internal class-ID.