Cannot handle multiple I2C devices on RPi 4B

[poirierlouis]

Context
Raspberry Pi : v4 Model B
pigpio C library : v78
Use multiple MCP23017 devices with I2C protocol.

Problem
When initializing multiple devices, first device with handle 0 (returned by i2cOpen) can be used without problem. I can write with i2cWriteByteData.
But using another device with handle 1, I can't write anymore as the library returns a PI_BAD_HANDLE error code when using i2cWriteByteData. While the call to i2cOpen for second device, returned a valid handle 1.

Example

#include "pigpio.h"

#define MCP23017_ADDRESS 0x20
#define MCP23017_IODIRA 0x00
#define MCP23017_IODIRB 0x01

#define I2C_BUS 1
#define I2C_FLAGS 0

int mcp[2];

if (gpioInitialise() == PI_INIT_FAILED) { return; }

mcp[0] = i2cOpen(I2C_BUS, MCP23017_ADDRESS | 0b000, I2C_FLAGS);
i2cWriteByteData(mcp[0], MCP23017_IODIRA, 0xFF);
i2cWriteByteData(mcp[0], MCP23017_IODIRB, 0xFF);

mcp[1] = i2cOpen(I2C_BUS, MCP23017_ADDRESS | 0b001, I2C_FLAGS);
i2cWriteByteData(mcp[1], MCP23017_IODIRA, 0xFF); // return PI_BAD_HANDLE
i2cWriteByteData(mcp[1], MCP23017_IODIRB, 0xFF);

Solution
After analyzing the code in pigpio.c. There is a mistake in the i2cOpen function :

pigpio/pigpio.c

Line 4119 in cc17196

i2cInfo[i].state = PI_I2C_OPENED;

.

You can fix it by replacing i with slot. I guess i is no longer in sync with slot after the loop. After changing it on local, I no longer have this issue.

[guymcswain]

Thanks for finding this. It'll be in the next release before the year end and in the develop branch sooner.

[guymcswain]

Fixed in v79