Mailboxes

Eric Anholt edited this page May 28, 2015 · 8 revisions

Overview

Mailboxes facilitate communication between the ARM and the VideoCore. This page lists the available mailboxes/channels. Each mailbox is an 8-deep FIFO of 32-bit words, which can be read (popped)/written (pushed) by the ARM and VC. Only mailbox 0's status can trigger interrupts on the ARM, so MB 0 is always for communication from VC to ARM and MB 1 is for ARM to VC. The ARM should never write MB 0 or read MB 1.

Channels

The following lists the currently defined mailbox channels, with links to pages describing the format of the messages.

Mailbox 0 defines the following channels:

0: Power management
1: Framebuffer
2: Virtual UART
3: VCHIQ
4: LEDs
5: Buttons
6: Touch screen
7:
8: Property tags (ARM -> VC)
9: Property tags (VC -> ARM)

Mailbox registers

The following table shows the register offsets for the different mailboxes. For a description of the procedure for using these registers to access a mailbox, see here.

Mailbox Peek  Read/Write  Status  Sender  Config
   0    0x10  0x00        0x18    0x14    0x1c
   1    0x30  0x20        0x38    0x34    0x3c