Teensy audio board schematic and simplified audio “board”

Dr Flywheel (aka Ron N7FTZ) has provided some details of the Teensy audio add-on board.  This is used in the upcoming JackAl add-on board expected to be available shortly, but can almost certainly be home-brewed by savvy constructors using the Teensy 3.6 and audio add-on board.

Here is the circuit diagram for the PJRC audio module:

The CODEC part is very much the reference design provided by the part manufacturer. The support for the EEPROM and the SD card is optional.

The libraries will be compatible with any SGTL5000 or for that matter a long list of other I2S compatible CODECs (look at the source code). If you are homebrewing an audio processor on the Teensy you should consider integration of the CODEC. The libraries will support the internal A/D-D/A of the Freescale ASIC with very few components (resistors, capacitors) added.

Sample resolution of 12-bits is sufficient for the type of audio DSP that we need, though the higher bit-rate CODECs are much better. It is a matter of cost effectiveness and board space.

An alternative simpler approach


Below shows mono circuits for a lower grade Teensy, however the circuit is the same for the Teensy V3.6 with the corresponding pins.

The input circuit (mono):

Here is the output circuit (mono):


New 5″ display for the Biteensio processor board

Jim W0EB latest µBITX has been  built with a 5″ RA8875 type Colour TFT display running on the BITeensio Card.

The system shown can be controlled by touching the screen, with an external USB Keyboard or an external USB mouse.  This almost completely eliminates the need for front panel controls and helps make a very clean looking µBITX build while keeping full functionality.

In using a 5″ or larger display, Jim and Ron have run into several problems . The 5″ display draws almost half an amp from the 3.3V rail and the even larger 7″ displays draw even more current. Using the 5″ display requires the BITeensio card to be modified to provide a high current, on-board 3.3 volt regulator as the Teensy 3.6’s on-board regulator would be severely strained trying to power this display.

In doing this we build the new 3.3V 1.5amp  regulator by isolating and using the pads for the 5 volt I2C bus on the card.  We do lose 5 volt I2C capability by doing this but the 3.3V I2C bus is still available so 3.3V I2C peripherals can still be used.

Another disadvantage of the larger display, other than its higher cost and higher current requirement, is that a fan is needed to cool the regulator’s heat sink. This makes retrofitting the bigger displays very difficult to say the least.

The Triumvirate Skonk Works has no plans at this stage to support any colour displays larger than the 5″ one.  Even this display is only for experienced experimenters, because of the mods that need to be done on the BITeensio card.

We’re also recommending that using the 5″ display be considered ONLY with a new BITeensio build rather than modifying a previously constructed one as there is much less chance of messing it up this way.

The modification instruction manual, with pictures is located in the “Documentation” directory of their website under the “Files” section. Like the previous 2.8″ Colour version and our older 4 Line I2C LCD display version, this version is capable of utilising an optional external USB keyboard for rig and CW control. Mouse control is only available with the Color TFT versions.

Rig control now allows use of a mouse for almost everything.   Purchasing an inexpensive, wireless keyboard/mouse combination will allow simultaneous keyboard and mouse operation. Using the keyboard or mouse for control, you won’t have to even touch the screen unless you want to. This will reduce wear and tear on the touch panel.

All documentation for modifying the BITeensio card and the just released firmware for the 5″ display version (ubitx_5_0_T_V1_00R.zip) is available on the TSW website in the files directory.

The 5″ display we use is the “ER-TFTM050-3 from Buy Display dot com.  If you decide to order one you need to get it with the 4 wire SPI interface, Resistive Touch Screen, 3.3V power option (5 V won’t work) and the ER3304-1 font chip. The SD card option is not  necessary  as all SD card  operation is contained  on the Teensy 3.6 itself.

Ordering information for the BITeensio kits is also available on the website and kits are in stock.