BQ78350-R1: how to read from the Manufacturer access using Block 0x44

Hi Scott,

Your command set is correct. Did you get a NACK signal durng Writing ?

You have to read from 0x44.

right now, I'm using an Atmel Studio 6 built driver so the Nack is extracted a bit, so effectively what I expect when I write anything over the SMBus is that the driver function returns the same data length that I sent it,

here's my write function if that helps

static bool BMS_MAC_dev_Read(mac_command* command)
{
	uint8_t msg[4] = { 0x44 , command->len , command->maccode , ( command->maccode >> 8 ) };
	uint8_t data[16];
	// make a check in io_write for the readonly
	if ( io_write(BMS_I2C_SMB_io, msg , 4 ) == 4 )
	{
		switch (command->access)
		{
			case BLOCK_R :
			        if ( io_write(BMS_I2C_SMB_io, 0x44 , 1 ) == 1 )
				{
				        if ( io_read(BMS_I2C_SMB_io, data, ( command->len + 3 ) ) == ( command->len + 3 ) )
					{
						sprintf(debug_buffer, "%x %x %x %x %x\n", data[0], data[1], data[2], data[3], data[4]);
						io_write(&EDBG_COM.io, debug_buffer, strlen(debug_buffer));
						while( usart_async_get_status(&EDBG_COM,NULL) == ERR_BUSY );
						// may need to do other stuff here
						return true;
					}
				}
		                break;
		}
	}
	return false;
}

So what happens is the second write of just 0x44 (or 0x00) to the bq doesn't work. I'm using it in a similar way to how the SMBus made simple guide does with comcodes which I'm supposing is why this isn't working for reads from 0x44. To clarify when I for example read voltage I use the following:

if ( io_write(BMS_I2C_SMB_io, &command->comcode, 1) == 1 )
	{
		if ( io_read(BMS_I2C_SMB_io, result, command->len) == command->len)
		{
			// may need to do other stuff here
			return true;
		}
	}
return false;

the comcode and len in the above for voltage is 0x09 and 2 respectively, and result is a uint8_t array to collect data recieved.

So with all that said, I'm not sure what a "read" from 0x44 means other than a write of 0x44 to the board then reading on the SMBus. feel like I'm missing something about the protocol.

Thanks for the reply btw and confirming what I've understood so far. The Battery Management Studio, Advanced Comm SMB isn't really good for explaining the underlying workings of the Manufacturer Access.

Thanks again,

Scott

Hi Scott,

I attached the file which responds your questions.

Scott.pdf