What I think would be a huge help is some sample code of a Master Master I2C bus using the handlers you define in the wire ISR functions.Welcome to our Instructables page. I assume those are internal registers you'd use for code written to run on that specific microcontroller not how to get it from another device. However, I do not recall seeing 0x99h in any packet dump. It looks like I2DAT is the register I want, at address 99h. The datasheet has several pages on I2C registers. I am pretty sure they used the same microcontroller in all the devices. The source device's 8 bit address is included as part of the communication protocol. Do I wire.end() and wire.begin() again with no address? But that means I am talking to it as a slave. wire.Begin() but if I use wire.Begin(7 bit address of the controller that all the devices talk to), I am able to get an ack back from the keypad when attempting to talk to it using the data from the packet captures. The packet captures do not contain anyīy the way, how do I join the I2C bus as a Master and have an address? Does an address matter on a master? I think it does in a Multi-master setup. I am at the point now where I need the other devices to talk to me, for example, the key pad. I can now control the display, but that is me talking to it. It has been very helpful figuring out the communication protocol (the layer on top of I2C) they use. Well, I do have some packet captures of the bus. How can that be helpful ? Without knowing what the bits in the registers are, you can not do much with it. Suppose the device is in Slave mode and it has registers and the register-address is only 8-bits, then it is not hard to write code that reads all registers. Is the device connected to something ? Is there is working I2C bus with data ? Do you have a logic analyzer ? What makes you think that the manufacturer will not tell what the registers are ? Did you try to ask them ?Īfter reading your question a few times, I still don't understand if the device is a I2C Master or a I2C Slave. What kind of device is it ? One of those smart power modules ? Or something for a car ? Because some devices have more than one I2C address. If you have a single I2C address, that is good information. When the device is a microcontroller, perhaps there are no registers, perhaps the data is written/read in a different way. It is even possible that the device will be damaged by writing wrong data to registers.

Arduino wire library internal register