SoftI2C primitive operations

[riteman]

Hello
I am working on a project where I need to access (read/write) data to an Artmel 24C32n eeprom. I have tried different libraries (mcauser and a modified version of peterhinch') but none of them work for me so I decided to use I2C primitives and develop a simple driver based on the datasheet from Atmel.
I read that only SoftI2C supports primitive operations which is the reason I import and use it.
I use Thonny 4.0.1 and micropython 1.19.1 running on a Raspberry Pi Pico W.

Here a snippet where I only read/write one byte:

import machine, time, ds1307
from machine import SoftI2C

i2c_addr = 0x57
i2c= SoftI2C(machine.Pin(1), machine.Pin(0), freq=100000, timeout = 50000) #max clock @ 3.3V
devices = i2c.scan()
print(len(devices))
for device in devices:
   print("Decimal address: ",device," | Hexa address: ",hex(device))

def EEWriteByte(address, bytedata):
    i2c.start()
    i2c.write(i2c_addr << 1) # add a write bit at the end
    NoOfACK = i2c.write(address >> 8)   #upper byte
    NoOfACK = i2c.write(address & 0xff) #lower byte
    NoOfACK = i2c.write(bytedata)
    i2c.stop()
    time.sleep_ms(20)    
    
def EEReadByte(address,buf):
    i2c.start()
    i2c.write(i2c_addr << 1)                       # add a write bit at the end
    NoOfACK = i2c.write(address >> 8)    #upper byte
    NoOfACK = i2c.write(address & 255)  #lower byte
    i2c.stop()
    i2c.start()
    i2c.write(i2c_addr << 1 + 1)               # add a read bit at the end
    i2c.readinto(buf, nack=True)
    i2c.stop()
    time.sleep_ms(20)
    return buf
    
buf = bytearray(1)
buf[0] = 0x55
print(buf)
EEWriteByte(0,buf)
print(EEReadByte(0,buf))  

When I try to run this snippet, I receive an error

Traceback (most recent call last):
File "", line 36, in
File "", line 13, in EEWriteByte
TypeError: object with buffer protocol required

The GO LE keys on my keyboard almost are worn out and still I have not been able to find the reason.

Any hint which can make this work ?

Regards

[robert-hh]

Lines like these i2c.write(i2c_addr << 1) are the reason, because you supply an integer as argument, but the call requires a buffer type argument, like a bytearray or bytes object. The same for the two following calls. You could use a bytearray of size 3, fill it with the data and then have a single write. Or use uctypes.pack, or ....

[robert-hh]

i2c.writeto_mem() and readfrom_mem_into() work now. It required a sleep after write. So that's the script now:

import machine, time, ds1307
from machine import SoftI2C

i2c_addr = 0x57
i2c= SoftI2C(sda=machine.Pin("SDA"), scl=machine.Pin("SCL"), freq=100000, timeout = 50000) #max clock @ 3.3V
devices = i2c.scan()
print(len(devices))
for device in devices:
   print("Decimal address: ",device," | Hexa address: ",hex(device))

buf = bytearray(1)
buf[0] = 0x63
print(buf)
i2c.writeto_mem(i2c_addr, 0x0003, buf, addrsize=16)
time.sleep_ms(20)
i2c.readfrom_mem_into(i2c_addr, 0x0003, buf, addrsize=16)
print(buf)

[riteman]

What does the addrsize = 16 mean. I do not use that parameter and it works fine

[robert-hh]

It tells, that the memory address is 16 bits long. You do not use it because you do not use i2c.writeto_mem() or i2c.readfrom_mem_into(). You have written your own versions of these methods.

[riteman]

Thanks!
I will try your version as well,,..

[riteman]

after some slight modifications it worked fine:

import machine, time
from machine import SoftI2C

i2c_addr = 0x57
i2c= SoftI2C(machine.Pin(1), machine.Pin(0), freq=100000, timeout = 50000) #max clock @ 3.3V
devices = i2c.scan()
print(len(devices))
for device in devices:
   print("Decimal address: ",device," | Hex address: ",hex(device))

buf = bytearray(1)
buf[0] = 0x63
print(buf)
i2c.writeto_mem(i2c_addr, 0x0003, buf, addrsize=16)
time.sleep_ms(20)
i2c.readfrom_mem_into(i2c_addr, 0x0003, buf, addrsize=16)
print(buf)

``

[riteman]

Hi I had no problem with the wiring and the SDA/SCL pinning was correct from the beginning or I would not have been able to scan the bus. The info about data from a bytearray being seen as an integer solved the problem - Using the type command I spent some time checking the difference between Buf[0] and Buf[0:1] ;-) The chip is an 8 bit eeprom and the address being read/written is split into 2 bytes and sent MSB followed by LSB Here the current version: ```py # MIT License # part of the code Copyright (c) 2018 Mike Causer # The wait routine is Copyright (c) 2019 Peter Hinch # Slightly modified import machine, time from machine import SoftI2C i2c= SoftI2C(machine.Pin(1), machine.Pin(0), freq=100000, timeout = 50000) #max clock @ 3.3V 100 kHz i2c_addr = 0x57 pages = 128 bpp = 32 # bytes per page WriteByte = 2*i2c_addr + 0 # this is the device address including the write bit as LSB (=0) ReadByte = 2*i2c_addr + 1 # and this is the device address with a Read bit (=1) WriteBytes = bytearray(3) Buf1 = bytearray(1) devices = i2c.scan() print('Number of units found: ',len(devices)) for device in devices: print("Decimal address: ",device," | Hex address: ",hex(device)) def Wait4ready(): # After a write, wait for device to become ready Buf1[0] = 0 while True: try: if i2c.writeto(i2c_addr, Buf1): # Poll ACK break except OSError: pass finally: time.sleep_ms(1) def read(addr, nbytes): RollOver = ((addr + nbytes) > 4094) #if we pass the 4 k boundary, the address-counter will roll over and start at address 0 """Read one or more bytes from the EEPROM starting from a specific address""" WriteBytes[0] = WriteByte WriteBytes[1] = addr >> 8 # first MSB is being sent out WriteBytes[2] = addr & 0xff # the LSb is sent i2c.start() # start a dummy write to set the address counter in the eeprom i2c.write(WriteBytes) # make a dummy write request (no STOP) Res = i2c.readfrom(i2c_addr, nbytes) # return data return Res def write(addr, buf): """Write one or more bytes to the EEPROM respecting the block boundaries """ RollOver = addr + len(buf) > 4095 offset = addr % bpp partial = 0 # partial page write if offset > 0: partial = bpp - offset WriteBytes[2] = addr & 0xff #isolate LSB of addr WriteBytes[1] = (addr >> 8) & 0xff #and MSB WriteBytes[0] = WriteByte #controlword for addressing EEPROM for write operations i2c.start() i2c.write(WriteBytes + buf[0:partial]) i2c.stop() #Now wait for the eeprom to finish the write cyclus Wait4ready() #time.sleep_ms(20) addr += partial # full page write for i in range(partial, len(buf), bpp): WriteBytes[2] = (addr + i-partial) & 0xff #isolate LSB of addr WriteBytes[1] = ((addr + i - partial) >> 8) & 0xff #and MSB WriteBytes[0] = WriteByte #controlword for addressing EEPROM for write operations i2c.start() i2c.write(WriteBytes + buf[i:i+bpp]) i2c.stop() Wait4ready() #time.sleep_ms(20) return RollOver EEprom = read(0,8) print('8 bytes read before write takes place: ', EEprom) Rollover = write(0,'Sed ut perspiciatis unde omnis iste natus error sit voluptatem accusantium doloremque laudantium ') print('Rollover during write operation? ', Rollover) EEprom = read(0,128) print('128 byte read: ', EEprom) ``` which results in the following output: Number of units found: 3 Decimal address: 60 | Hex address: 0x3c Decimal address: 87 | Hex address: 0x57 Decimal address: 104 | Hex address: 0x68 8 bytes read before write takes place: b'Sed ut p' Rollover during write operation? False 128 byte read: b'Sed ut perspiciatis unde omnis iste natus error sit voluptatem accusantium doloremque laudantium cdefghijklmnopqrstuvwxyz012345' Thanks for all the good answers and amount of work invested. It's very much appreciated! Regards

[hardikofficial963]

Issue:
I2C Scan on ESP32-S3 Returns No Devices

Description:
I am trying to scan for I2C devices on the ESP32-S3 using MicroPython but getting no devices detected, even though the hardware works with the Arduino Wire Scan example.

MicroPython Version:
v1.24.0 (2024-10-25)

Hardware Details:

• Microcontroller: ESP32-S3
• I2C Device: PCA9685
• Pins Used:
  • SCL: GPIO 19
  • SDA: GPIO 20

Code:

    from machine import Pin, SoftI2C
    import time
    
    def scan_i2c_addresses():
        # Initialize I2C
        i2c = SoftI2C(sda=Pin(19), scl=Pin(20), freq=400000)
        
        print("Scanning I2C addresses...")
        devices = i2c.scan()
        
        if len(devices) == 0:
            print("No I2C devices found!")
        else:
            print(f"Found {len(devices)} I2C devices:")
            for device in devices:
                print(f"Device address: {hex(device)}")
    
    if __name__ == '__main__':
        scan_i2c_addresses()

Observations:

• Expected Behavior: Detect the PCA9685 at address 0x40.
• Actual Behavior: "No I2C devices found!" message is printed.

Troubleshooting Performed

1. Tested the same hardware and wiring configuration using the Arduino Wire Scan example. The device at 0x40 is detected successfully.
2. Verified the wiring connections:
   SCL → GPIO 19
   SDA → GPIO 20
3. Proper pull-up resistors in place.

Request:

• Is there a known issue with SoftI2C on ESP32-S3 in MicroPython?
• Are there any additional configurations or debugging steps I should try?

Any insights would be appreciated.

[peterhinch]

Please see my response to your issue in the MP bug tracker.