About some I2CTarget constructor parameters question.

[water5]

class machine.I2CTarget(id, addr, *, addrsize=7, mem=None, mem_addrsize=8, scl=None, sda=None)

What mean addrsize and mem_addrsize? please post example to explain, thanks.

[fdufnews]

The answers are in the MicroPython documentation
https://docs.micropython.org/en/latest/library/machine.I2CTarget.html

[sosi-deadeye]

I2C devices have an 7 or 8 or 10 bit address. Supported are 7 and 10 bit address size or maybe the 8 is missing in the docs.
To address a memory, an index is required. Valid values are 0, 8, 16, 24 and 32.

I guess if the mem_addrsize is 0, you could not access directly an address.
8 allows addressing 256 bytes
16 allows addressing 65536 bytes
...

I've never used it. Maybe it's easier to understand with a real example: https://ww1.microchip.com/downloads/aemDocuments/documents/MPD/ProductDocuments/DataSheets/24AA08-24LC08B-24FC08-8K-I2C-Serial-EEPROM-DS20001710.pdf

This EEPROM has an addrsize=7 and mem_addrsize=16

[fdufnews]

MicroPython documentation says:

I2C.scan() :Scan all I2C addresses between 0x08 and 0x77 inclusive

So there is no chance it can find a 10 bit address peripheral.

If you want more information on how 10 bit addressing works read §3.1.11 in the following document
https://www.nxp.com/docs/en/user-guide/UM10204.pdf

[water5]

I2C controller side

from machine import Pin, I2C
i2c = I2C(1, scl = Pin(25), sda = Pin(26), freq = 400000)
i2c.writeto(67, b'1234')

4

---

I2C target side use different mem_addrsize value,

i2c_mem = bytearray(5)
i2c_target = I2CTarget(0, scl = Pin(1), sda = Pin(0), addr = 67, mem_addrsize = 0, mem = i2c_mem)
i2c_mem

bytearray(b'1234\x00')

i2c_mem = bytearray(5)
i2c_target = I2CTarget(0, scl = Pin(1), sda = Pin(0), addr = 67, mem_addrsize = 8, mem = i2c_mem)
i2c_mem

bytearray(b'34\x00\x002')

i2c_mem = bytearray(5)
i2c_target = I2CTarget(0, scl = Pin(1), sda = Pin(0), addr = 67, mem_addrsize = 16, mem = i2c_mem)
i2c_mem

bytearray(b'4\x00\x00\x003')

i2c_mem = bytearray(5)
i2c_target = I2CTarget(0, scl = Pin(1), sda = Pin(0), addr = 67, mem_addrsize = 24, mem = i2c_mem)
i2c_mem

bytearray(b'4\x00\x00\x00\x00')

i2c_mem = bytearray(5)
i2c_target = I2CTarget(0, scl = Pin(1), sda = Pin(0), addr = 67, mem_addrsize = 32, mem = i2c_mem)
i2c_mem

bytearray(b'\x00\x00\x00\x00\x00')

[robert-hh]

Please use i2c.writeto_mem at the controller side.
Edit: AFAIK the current default support for I2C_target supports only mem_addrsize=8.

[water5]

What difference between category standard bus operations and memory operations?

Specified mem parameter(backing memory) when construct I2CTarget object, controller
side should be use writeto_mem, because I2CTarget has actual memory address.

controller side

i2c.writeto_mem(67, 5, b'abc')

target side

i2c_mem = bytearray(10)
i2c_target = I2CTarget(0, scl = Pin(1), sda = Pin(0), addr = 67, mem = i2c_mem)
i2c_mem

bytearray(b'\x00\x00\x00\x00\x00abc\x00\x00')

---

If not specified mem parameter(backing memory) when construct I2CTarget object, then
use I2CTarget.readinto(buf) read to external buffer(not have actual memory address),
result incorrect. controller side should be use writeto().

controller side

i2c1.writeto_mem(67, 5, b'abc')

target side

i2c_target = I2CTarget(0, scl = Pin(1), sda = Pin(0), addr = 67)

def i2c_target_irq_handler(i2c_target, buf_ = bytearray(10)):
	flags = i2c_target.irq().flags()
	if flags & I2CTarget.IRQ_WRITE_REQ:
		i2c_target.readinto(buf_)
	if flags & I2CTarget.IRQ_END_WRITE:
		print(buf_)

i2c_target.irq(i2c_target_irq_handler, trigger = (I2CTarget.IRQ_WRITE_REQ | I2CTarget.IRQ_END_WRITE), hard = True)

bytearray(b'\x05abc\x00\x00\x00\x00\x00\x00')

Is it understand right?

But in this case, how return buf_?

[beetlegigg]

I think you simply get the master to read the slave memory rather than returning a value.
In the i2c master read the 10 bytes of the bytearray like -
result = i2c.readfrom_mem(67,0,10)
An hour of so back I attempted to answer a query from someone about the I2cTarget by giving example code in the rpi micropython forum, so here's a link to that example code where the i2c master both writes and reads to an i2c slave in case its of interest.
https://forums.raspberrypi.com/viewtopic.php?t=395785&sid=3289fd45da061d9a0c04415e91667f49

[fdufnews]

I2C devices have an 7 or 8 or 10 bit address.

Well, I2C standard only defines 7 and 10 bits. the eighth one is the data direction.