I2C smbus2 block data - Raspberry Pi Forums

hello, i'm working on project exchanging data between rpi , arduino, , have been forced switch i2c communication protocol several reasons. i've had success using simple read , write requests pass single bytes of data , forth. i'm trying pass bunch of bytes, i'm trying use read_i2c_block_data smbus2 library. continue following error no matter try:

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traceback (most recent call last):   file "/home/pi/sketchbook/i2ctalk04/i2ctalk04.py", line 36, in <module>     readbunchofdata(4)   file "/home/pi/sketchbook/i2ctalk04/i2ctalk04.py", line 25, in readbunchofdata     mydatahere = readblockdata(numbytes)   file "/home/pi/sketchbook/i2ctalk04/i2ctalk04.py", line 17, in readblockdata     x = bus.read_i2c_block_data(address, 0, numbytes)   file "/usr/local/lib/python3.4/dist-packages/smbus2/smbus2.py", line 391, in read_i2c_block_data     ioctl(self.fd, i2c_smbus, msg) oserror: [errno 121] remote i/o error

line 17 " x = bus.read_i2c_block_data(address, 0, numbytes)" line. i've read related there being nothing on other end of i2c bus, can't see problem is. i've tried several different ways of doing read_i2c_block_data , similar limited examples i've found. suggestion appreciated. many thanks.

here code pi:

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from smbus2 import smbus import time  bus = smbus(1) address = 0x04  def writenumber(value):     bus.write_byte(address, value)     return -1  def readnumber():     number = bus.read_byte(address)     return number  def readblockdata(numbytes):     res3 = []     x = bus.read_i2c_block_data(address, 0, numbytes)     res3.extend(x)     return res3  def readbunchofdata(numbytes):     # send number of bytes requesting     writenumber(numbytes)     # receive data     mydatahere = readblockdata(numbytes)     # show we've got     print ("we received ", numbytes, " of data")     in range(0, numbytes):         print (mydatahere[i])           while true:     # now, hard-code 4 bytes of data     print ()     print ("we requesting ", 4, " bytes of data")     readbunchofdata(4)     print () 

here arduino code:

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#include <wire.h>  #define slave_address 0x04 int number = 0; int datano = 0;  void setup() {   serial.begin(9600);   wire.begin(slave_address);      wire.onreceive(receivedata);   wire.onrequest(senddata);      serial.println("ready!"); }  void loop() {   doingsomething(10); }  void doingsomething(int loops) {   (int = 0; i<loops; i++) {     serial.print("i'm doing else...");     serial.println(i);     delay(50);   } }  void receivedata(int bytecount) {   while(wire.available()) {     number = wire.read();          if (datano == 0) {       // datano, how many bytes send - hard-coded @ 4       datano = number;     }     else {       // should not here       serial.println("we got hole 1");     }     } }  void senddata() {   byte output[] = {0x01,0x02,0x03,0x04};  // sample data testing   wire.write(output, 4);   datano = 0; } 

normally pass 3 values bus.write_byte function, i2c address register address data

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