Assignment 22 - MIDI out to STM32 Device

USB Setup Forum That Helped a Bit

• Experiment Design: Take in a USB input data, say MIDI data, from an external source (PC/Laptop/MIDI Device) and output

The device (STM) to be a USB Host, but what is a USB host?

Main Points on USB Hosting

There are multiple USB host types. Since we are doing a USB-type B from our device, and USB-type A to our STM, we want our STM to be an OTG A-host.

Some behaviors to note are that:

• The STM has a OTG_HPRT status register for host port control, that
• ... (really a lot of the behaviors are "as you need them" so follow the OTG_FS programming model for whatever you need, and look up stuff as you go).

Initialization

When connecting:

• If an "A" plug is connected, then the device enters host mode, if "B" then enters device mode.
• You must follow the following to initialize the device in this way
  • OTG_GAHBCFG:
    • Global interrupt mask bit OTG_GINTMSK = 1
    • Empty the FIFO Rx bit via RXFLVL within the OTG_GINTSTS register.
    • Program the same Tx bit TXFLVL in the same register.
  • OTG_GUSBCFG:
    • Enable some of HNP, SRP
    • OTG_FS timeout calibration field
    • USB turnaround time field (in OTG_GUSBCFG)
  • Unmask OTG_GINMSK and either choose to mask or not the OTG interrupt and mode mismatch interrupt masks
  • Read from the CMOD bit in OTG_GINSTS to confirm that we are in the host mode (or device mode if you want that)

Host Initialization

You must:

• Program HPRTINT in the OTG_GINTMSK register to unmask
• Set OTG_HCFGregister to select full-speed host
• Set OTG_HPRT to 1, to drive V_BUS on the USB (we want to power it from here).
• (continue from pg. 1782)

Channel Initialization

You'll need to setup a USB channel in order to read and write data over. See pg. 1783 for that.

Receiving Data Packets

See pg. 1784 and 1785 for read and write access to FIFOs per channel. The programming flowchart is essentially what code you want to have to setup your USB read/write functions.

Setting up GPIO

By ![[datasheet_stm32l476rg.pdf#page=99]]
use the PA10-13 pins for connecting the USB-A side pins to, rather than the onboard usb (that's the debug USB). Via ![[datasheet_stm32l476rg.pdf#page=99]]
,