 Okay today we are going to exercise the mailbox feature of the SD25DV and to do that we are going to use the SD25R3911B discovery board and also we are using the SD25DV discovery board as well. Remember that to use the mailbox features we must power the SD25DV because the registers of RAM like buffer requires power digital power versus the fact that the EE problem on the SD25DV can be powered via RF in passive mode. So when you first started the SD25R3911B discovery GUI you'll be greeted with a screen that looks like this. You would first start do a demo board check, calibrate antenna, a chest regulator. Now you can put the red board on top of the green board make sure that you don't have any kind of shorting because we are talking about open not package devices. When you do that you will run a tab called SD25 tag editor and when you do that it will take some time and it will give you this this panel. You go to dynamic tag you choose the SD25DV04K. To see if the reader and the tags are in connection you do an inventory as you can see you see the UID of the SD25DV. Now the next thing you have to do you're going to change some configuration registers in the SD25DV you basically enable the mailbox features. To do that you first have to present the password because it requires password to change or edit the status configuration of the SD25DV. Click on password then present password and it's all zero and I'm using the default password all zero. I present password it say no error during present password so I'm good right there. Now going back to configuration register I'm going to read configuration and you notice that I already have mailbox mode enabled but normally when you're in the default condition when the device is first available it is come as default of value of zero. I'm going to reset that value so that I can show you the reading and writing of this bit. So go to write configuration and I'm going to fill with zero. Write configuration and it say done. When I read the configuration status again notice that the mailbox is now disabled. So this is the default condition of the SD25DV. Now we are going to change it to one so we can enable the mailbox. Go to write configuration again. Go to zero one. Write configuration. Now we're going to read configuration or static register. You go to MB mailbox mode. You see that it's enabled. Now you're going to the tab called the FTM. So here we are in the FTM tab. When you first have it and you do a read dynamic configuration all the bit will be zero. Even the MB enabled bit is zero as well. You first have to change this bit to one so that you can read and write to the mailbox because it doesn't mean you enable it. First you have to present the password. Present password so you can change that bit. Say no error doing present password. Go back to your FTM. Write bit one. So now bit one is enabled. I'm going to write 16 bytes to the 256 byte buffer. 16 or 32 or 8 or 4 but here 16 just a sweet 16 number here. So I'm going to write with 16. Okay when I read back I read back the 16 bytes. Now the reality is that now the buffer is full. You do a read dynamic configuration. You see that is there's a put message flag right here. And if it's full you cannot write it again. Let me show you that. So you want to do a write message again. Say this time you put 33 for example. You write. It's going to give you an error. It's the error because the way the mailbox works is that if the buffer is full the I2C section has to offload the message and then clear out the flag. Once the reading process occurred on I2C it will clear out the flag. So the data is still there. So you cannot write on top of it. It's kind of a good secure way so you cannot accidentally RF writing over and over again this place. So we'll give you an error for sure. So I'm because I don't have I2C connected and do all these arbitration right now. I will just basically reset the MB bit and be enabled it. And that will basically reset the configuration basically empty out the content of the mailbox. So I go to present password again. Present password. And I go to fast transfer mode. I write dynamic configuration. I'm going to zero that out. So now it's zero. I'm going to re-enable MB enable bit because it's important so that I can write it again. Correct because it's disabled right now. So right back zero one right configuration now mailbox is enabled the rest are zero so it's a clean slate again. Now I want to do a write message and I want to write with say BB for example so it doesn't give me an error anymore. I can read back the message BB. So basically the mailbox features is designed so that you can have a dual access the dual interface access between RF and I2C. It's not really there for passive operation because you will have non-volatile storage to do that. So it doesn't make sense just to read and write to a non-volatile storage without somebody else on the other end accessing it. Okay thank you.