Mailboxes

Surafel Assefa edited this page May 2, 2018 · 10 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 Read/Write Peek  Sender  Status    Config
   0    0x00       0x10  0x14    0x18      0x1c
   1    0x20       0x30  0x34    0x38      0x3c
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