I want to share my experience in upgrading firmware in AVR-889. As you probably know, unlike 2309 it does not have external serial port, which can be used for firmware upgrade. Official word is send it to service center if upgrade is needed. For many it could be a right choice, but for me local service center wanted to see purchase receipt before accepting receiver under warranty. Unfortunately I couldn't find a copy in my archive, and service center refused to do work. Thus I had either pay for it or do it myself. I decided to go second way. I should warn everyone, that this task is not for regular person, who is not familiar with electronic devices and computers.
I obtained a copy of service manual (which actually covers both 2309 and 889 - they are almost exactly the same unit). I found that 889 has the same boards as 2309, just few part related to RS232 port are not soldered on the the main CPU board. But when I looked closer, it was clear that I still can connect computer to a receiver. Initially I thought that I can use service port on main CPU board CX901 (see first picture), but it became clear that this port only lets me talk to a main CPU. But upgrade includes firmware for main and sub processors and DSP. After I looked closer, I found that if I connect computer to port CY061 on digital board, I can imitate the way it works with 2309 model (see second picture). Circuits MO232CI and MI232CO are what I need to connect to. I also have to supply 5V power to 232C5V circuit.
Unlike regular RS232, to connect computer to 889, you need TTL level serial interface. You can buy one for $10-15. Since I do not have RS232 port in my computer I used USB to RS232 TTL converter http://www.ftdichip.com/Products/Eva...s/TTL-232R.htm
Make sure you get a 5V one, 3.3V version will not work. As I said, I needed to supply +5V to the port, I used VCC pin in CX901, and just connected it with wire to 232C5V circuit. I connected ground wire from RS232 converter to pin GND in CX901 (CY061 port does not have ground circuit). Then I connected receiver of RS232 interface to circuit MO232CI and transmitter to circuit MI232CO. See pictures 3, 4 and 5.
You can verify if everything is correct, using terminal program on your computer. In Windows XP it is Hyperterm. Connect it to the serial port with settings: speed 9600, 1 stop bit, no parity, no flow control. If everything is good, when you turn on your receiver you will see messages from it about current operation mode. It also reports when you change source or volume.
I want to warn you make all connections only when receiver it turned off (completely, not just in stand by mode), otherwise you can damage it!
When everything is ready turn on receiver, and start firmware update program. It runs for like 15 minutes, and upgrades main CPU first then sub-CPU and at last DSP. DSP step takes most of time.
When upgrade is complete, just turn off receiver, disconnect all wires and put cover back on. You are done.