Received I2C data is mangled #8390
Description
CircuitPython version
Adafruit CircuitPython 8.2.4 on 2023-08-22; TinyS3 with ESP32S3Code/REPL
import time
import board
from adafruit_bus_device.i2c_device import I2CDevice
def read_i2c(send="123"):
ret = "nothing"
try:
with board.I2C() as i2c:
device = I2CDevice(i2c, 0x08)
br = bytearray('yyyyyy', 'ascii')
with device:
print(f"sending {send}")
device.write_then_readinto(send, br)
ret = br
except Exception as e:
print(f"{type(e)}: {e}")
return ret
send = bytearray(1)
send = "123"
while True:
print("I2Cing in 1 second...")
time.sleep(1)
r = read_i2c(send)
print(f"Sent {send}, got {r}")
time.sleep(5)Behavior
Posting as an issue as suggested at https://forums.adafruit.com/viewtopic.php?p=985515#p985515
The printed output should be
Sent 123, got bytearray(b'3\x00\x00\x00\x00\x00')
But instead is
bytearray(b'"\x00\x00\x00\x00\x00')
Description
No response
Additional information
I am sending some code over I2C to an ATTiny85 which is configured with a sketch to read it all in, then send back 6 bytes, the first of which is the final byte from the sent code. The idea was just to confirm that I could get I2C to work between the two chips, but CircuitPython seems to mangling the received the code.
The code running on the ATTiny is:
#include <Wire.h>
char rcvd = 0;
void setup() {
Wire.begin(8); // join i2c bus with address #8
Wire.onReceive(receiveEvent); // register event
Wire.onRequest(requestEvent); // register event
}
void loop() {
delay(100);
}
void receiveEvent(int howMany) {
while (1 < Wire.available()) { // loop through all but the last
char c = Wire.read(); // receive byte as a character
}
rcvd = Wire.read(); // receive byte as an integer
}
void requestEvent() {
char buf[6] = "xxxxxx";
sprintf(buf, "%c ", rcvd);
Wire.write(buf); // respond with message of 6 bytes
}
Running Arduino on the TinyS3 with a sketch to do similar to the CircuitPython behaves correctly. Here is that sketch:
#include <Wire.h>
void setup() {
Serial.begin(9600);
Wire.begin(7); // join i2c bus (address optional for master)
Wire.onReceive(receiveEvent);
}
byte x = 0;
void loop() {
Serial.println("I2Cing in 1 second...");
delay(1000);
Wire.beginTransmission(8); // transmit to device #8
Wire.write("123"); // sends five bytes
Wire.endTransmission(false); // stop transmitting
Wire.requestFrom(8, 6); // request 6 bytes from slave device #8
Serial.print("Sent 123, received ");
while (Wire.available()) { // slave may send less than requested
char c = Wire.read(); // receive a byte as character
Serial.print("\\x");
Serial.print(c, HEX); // print the character
}
Wire.endTransmission();
Serial.print("\n");
delay(5000);
}
void receiveEvent(int howMany) {
while (1 < Wire.available()) { // loop through all but the last
char c = Wire.read(); // receive byte as a character
Serial.print(c); // print the character
}
int x = Wire.read(); // receive byte as an integer
Serial.println(x); // print the integer
}
Which gives the expected output:
Sent 123, received \x33\x20\x20\x20\x20\x20
Further, using a login analyzer on the I2C pins shows the correct data on the wire.