Wednesday, 19 November 2014

BlueFlyVario_TTL_GPS_v10 released

I am pleased to release the first of the version 10 Bluefly's. Today I have begun shipping back orders for the BlueFlyVario_TTL_GPS_v10. The previous blog post indicated that these were on the way and described the other models under development.

The BlueFlyVario_TTL_GPS_v10 is primarily designed for integration onto the Kobo, although some people will use it with other e-Readers or just for experimenting. See this older blog post for a step by step guide which describes how to install it on the Kobo mini. The procedure is pretty much the same for this updated vario. The simple case described in this earlier post which you can 3d print will still fit, but you will need to drill a small hole for the new button. 

What is in the bag?

Everyone installs their vario in a slightly different way. In the little bag are the following components:
  • The main module. The PCB size is 50mm x 17 mm which is the same as the v9.
  • A small piece of neoprene. This is really important. It must be placed over the pressure sensor if the sensor is exposed to any light (even light through a translucent case). The neoprene allows the air pressure through, but stops the light. Light makes the pressure sensor go crazy.
  • Some clear PVC heat shrink cut to size. It is fine to install the module without a case if you use the heatshink.
    • Poke a small hole through one side of the heatshrink just big enough for the button.
    • Put the neoprene on the pressure sensor, and the heatshrink evenly over the module.
    • Use a heat gun, or a hairdryer on hot setting to carefully shrink the plastic around the module.
  • A 4x1P right angled header. Some people solder the wires directly to the module, others use the header so it is easy to remove for testing. If you use the header I suggest you trim the through-hole pins to the thickness of the PCB so they are flush with the bottom of the board.
  • A 4x1P DuPont connector with 20 cm wires. This will fit in the header, and the wires connect to the serial port of the Kobo. You should trim the wires to be as short as possible so you minimise stray voltages.

New Hardware Features
Since the BlueFlyVario_TTL_GPS_v9 there have been a few hardware changes. Refer to the circuit diagram and PCB layout below.
  • Button. This is the biggest change with the v10 BlueFly's. The button provides soft power on/off by controlling the shutdown pin of the TC1015 voltage regulator. When pressed the shutdown pin of the regulator is connected to the supply voltage via the diode, which turns on the regulator and powers the micro-controller. One of the first things the micro-controller does is keep the shutdown pin of the regulator turned on. The small diode in conjunction with the 10k pull down resistor then allows another pin on the micro-controller to sense button presses. The behaviour of the button is programmed like this:
    • When the module is off, a short press will provide soft power-on as described above. The module will do the start up beep thing.
    • When on, short presses will turn the audio on an off. A short beep provides confirmation.
    • When on, a long press (2 sec) will power the module off.
  • Solder Jumper. Some people will want the module to power on as soon as power is supplied to the module (that was the behaviour of the v9). By closing the solder jumper with a dab of solder the shutdown pin is permanently biased to the supply voltage. You can still use the short presses on the button to turn the audio on/off. A long press will turn the module off, then it restarts in six seconds.
  • Thinner PCB with gold contacts. I changed to a thinner 4-layer PCB to optimise component placement. ENIG contacts provide a cleaner finish.
  • Additional capacitance on power. I added an additional 1uF capacitor to the supply voltage line. This will reduce stray voltages in the supply if you have longer wires, which should improve GPS performance, but I still recommend trimming your wires as short as possible.
  • UART TLL resistors. The resistors in series with the Tx and Rx lines on prevent the module being powered on by stray voltage. I selected 2.2k based on trial and error. These values work with the Kobo and with FTDI based USB to serial converters.
  • Exposed U1 pins under the GPS. The second serial port on the microcontroller is connected directly to the PA6H GPS. If you are a super electronics hacker and want to update the firmware on the GPS then you can use this serial port for a temporary connection.
  • Exposed speaker pins. Some people want to wire in a different speaker. The pins in parallel to the speaker make this a little easier.

New Firmware Features

There have been a bunch of changes to the firmware to accommodate the new hardware and incorporate some new features. Some key changes:
  • The firmware now includes a modified version of the ds30loader bootloader. This will allow future firmware updates if you connect the module to a PC using a USB to TTL serial converter. The bootloader mode is entered by powering on the module with programming pads 2 and 5 shorted together. I will produce a more fulsome description of the firmware upgrade procedure in later posts.
  • There is now an auto power off feature. Essentially, if the module has not moved more than a certain number of meters vertically for a set duration then it will power down. The default settings are 2 m (20 dm) vertical movement in 10 minutes. You can adjust these settings like other hardware settings. I will update the hardware settings manual and BFV Desktop app at some stage.
Next Steps

I am working on release of the Bluetooth_v10 and the USB_v10 over the coming weeks, in conjunction with catching up on back orders and trying to keep on top of the rest of my life. Please be a little patient if you are waiting on a back order.