CPU Board

CPU / User Interface Control Board

Sections on the CPU / Display board. See also the photo below.

The CPU / Display board board sections. A basic setup can exclude the USB Hub and VFO Si5351. The VFO Si5351 is best to have on the Radio board, but the layout was left on this board as it can be used for an oscillator from a few kHz to over 150mHz and used as a signal source for other projects or the basis for a Signal Generator. More options here a) for a Si5351 module sub board sold cheaply having three outputs , or an on board Si5351 is and a TCXO for an oscillator with very low drift. Two SMA Coax sockets are provided for outputs.

Features in full

  • 2 x Arduino NANO controllers. If USB and remote CAT is required the Master NANO needs to be upgraded to an Arduino EVERY.
  • 20 button Keypad (a sub board with 3-wire connection)
  • 20 x 4 line LCD or TFT colour display (The TFT software is to follow)
  • Digital glue logic and radio function control interfaces
  • 2 x Rotary controls, Tuning control (400ppr) and Functions control
  • USB 4 port hub for interact to a PC (etc) using USB (optional) for CAT control (CAT software to follow)
  • USB sound card for audio input and output to computer using USB
  • A sturdy rear mounted USB-B connection to your desktop / laptop computer connection
  • The board also has layout to add a Si5351 IC and TCXO, or a standard Si5351 sub-board. This is an extra and not normally for the functionality in this project. It can be used to design a general purpose oscillator, local oscillator for other projects, or the basis for a signal generator (create your own software!).
  • Spare I2C connections


Option Choices. First of all decide what options you want / need. You can change or add at a later stage, so starting simple might be a good option. The options are:

  • 320 x 240 3.2″ COLOUR TFT display is now the only display option. The colour TFT worked out so well and initial orders are for the TFT option only, do the basic 4 line LCD has been dropped (it is a game to keep the software up to date for both).
  • USB Hub. If you don’t need remote computer CAT control then this will not be needed.
  • Si5351 Oscillator. This is legacy, and there is one on this board but it is not needed for the HamPi. It was left on the board so that as a separate project constructors could use it for things like a Signal Generator, or their own radio. This is NOT software supported.

Construction and mounting of the KeyPad

  • Mount all of the buttons to the REAR of the board. and the other parts to the front of the board.
  • … more following

CPU Board construction and mounting

  • First solder on the GL850G USB hub IC, and 12mHx XTAL chip. A normal HC47U XTAL or similar will also work, and easier to mount. This will probably be the most challenging part of this board build. It is tiny! If you have never soldered these before I suggest you get a friend to so it, one with very good eyesight. If you have a tiny heat gun, all of this will make the job is made a lot easier. Apply solder paste, or semi-liquid flux and pre-tin the PCB fingers. Now check the leads on the GL850G to ensure they are really bright, clean and straight. If not then these will need tinning and fluxing too. (I actually rubbed the bottom of the pins lightly on fine wet-or-dry!) If is goes wrong use solder braid to remove excess solder. Apply a little flux to the 28 pins (Dip the pins in the flux!). Next mount the GL850G with the heat gun, ensuring it is the correct way around. If no heat gun, just place in position and with a tiny iron bit and push two of the corner legs down so the solder pre-applied flows. Next ensure all is straight, and apply heat to all the other pins by simply pressing them down with the iron bit. I have done a few now and it is not easy but it can be done. When all done I used a scalpel edge to see if each pin was soldered well and not loose. If it moves aside it needs more work. Now solder down the XTAL chip, apply solder from the corners. Phew…! Later on the XTAL oscillator can be seen working on an oscilloscope, when a USB device is plugged in. The GL850g can go into standby and shut clock down when there is nothing connected. It is good to mount all the parts associated with the USB option and test it before preceding to complete the rest of the board. The USB hub is powered from the host (Upstream device) when plugging it in. I.E. Your PC computer.
  • Now fit all other SMD devices. This will be easier. Look at the Silk Screen for orientation of FETS and diodes.
  • Next fit the other parts. I always fit low parts and electrolytic caps last, as they are easy to burn with the side of the iron.
  • NOTE: Some parts are fitted to the back of the boards. These are button switches, 3 x LEDS, TFT display and Rotary Function control. More on these later.
  • Do not fit parts associated with the Si5351 on the top LHS of the board. This is an unused option.
  • The two Nano’s and the TFT Display are mounted into socket strips which is 8mm high. (See pictures). The TFT socket strip is on the REAR of the board. Do not mount the LEDs yet, but put them on the reverse side of the board with the legs sticking through (the right way around. The leads with the flat edge in the plastic go to ground), ad bend the led legs without soldering them. This will hold them in place so they don’t fall out. Later on when the TFT s secured and the CPU mounted to the front panel and spaced correctly, the LEDs are positioned so they protrude through the Front Panel and only then soldered in place.
  • Fit the smaller Rotary Encoder to the rear of the board. Note the two solder short pads next to it on the reverse of the board. These are to carer for different types of encoders and some are in reverse. These pads swap the direction of rotation. When all it powered up and the display working, add solder to these pads to connect up the encoder.
  • The Master NANO is a NANO EVERY and the SLAVE is a standard NANO.
  • When all the parts are fitted to the top of the board, the TFT can be plugged into the back, and two 10mm spacers and nylon screws and nuts used to mount it to the CPU board. Just use the two mounting holes furthest away from the connector for this. (The other holes are not needed, and the TFT holes are very close to the glass, and not worth using).
  • Next the CPU Board can be mounted to the front panel. This is done with 4 M3 or 6BA screws 22 to 25mm long. The usual steel M3screws can be used but the heads will need to be pre-tinned with solder. The other option is to use 4 6BA brass screws. These are easier to solder. (I have used both with complete success). Using 8 nuts, 4 either side of the CUP PCB, mount the 4 screws from the rear of the board, so the heads of the screws is exactly level with the front of the TFT glass. Finally offer up the TFT to the front panel and align it with the hole in the Front panel for the TFT, and note where the top RRS of the display glass needs to be, and solder the screw head of that one screw in place to the Front Panel. If this one corner is in the correst place, the next screw can be soldered in place (The top LHS). Check the TFT is lined up well, and if all good solder the other two screw heads in place, allowing the solder to flow around at least half of the head of the screw.
  • Now solder the LEDs in place as already described.
  • At this time there is no bezel for the TFT, so if you have any resources / clever friends, her is an opportunity. (This is not the area of my expertise).
  • … more following

Any errors found or improvement suggestions please email them in, appreciated.