Homebrew-radios.net - TrxAVR - minimum components for early testing

Some builders might wish to assemble their TrxAVR board in a way that allows testing of USB connectivity
and ATmega2560 programming at an early stage in the programming.
The advantages of doing this are:

• It gives confidence that the system works before installing the remaining components.
• If there is a hardware fault (eg: non-soldered ATmega2560 or FT245R pin) then it is easy
  to trace because there are few components to check.

My rig uses a home-made TrxAVR-A controller.
I needed to assemble one of Glenn's TrxAVR-B boards to test a prototype Colour TFT board.
(designed by Chris Stake, drawn up and manuactured by Glenn and programmed by Gerard)
The connection to the colour TFT display I2C is 3 wires: data, clock and ground. There is a 4 pin
I2C bus connector adjacent to the 24LC512 EEPROM for this and other I2C devices.
So I didn't need the parallel display connecting components.

Even without a display connnected, the minimum configuration described below allows you to:

• Test USB connectivity
• Use Mprog to configure the FT245R USB chip.
• Observe that Hobcat reports: USB: TrxAVR control baord (FT245R) s/n A9RUL680 etc
• Connect the AVR programmer (AVRISP2 or Ponyprog)
• Set the fuses and program the Atmega2560.
• Observe the message: TrxAVR v 1.38 ready (no DSP load delay delay until DSP code loaded)
• Run Hobcat's Hardware setup screen and configure (Do not specfiy a colour TFT dispaly unless
  you have one connected - the repeated I2C waits will slow the processor)
• Observe meaningful data in Hobcat's debug screen. (The variable names all come from TrxAVR)
• Load DSP code and parameters (C:\TrxAVR folder needed - set up same as C:\Star + trxavreemem.ini)
• Reboot and obvserve 20second DSP load delay (can't see it as you have no display)
  (No DSP unit needed)
• Run Hobcat's DSP window and see meaningful parameter values received via USB from TrxAVR.
• Use Hobcat to upload stacks, slots and other data from trxavreemem.ini.
• Use Hobcat to upload default SWR forward and reflected claibration data - observe correct checksums.
• Use Hobcat to upload AD603 calibration curve (used by DSP monitor)
• Run Hobcat's DDS window and see meaningful VFO A and B frequencies. Band and mode changing
  should work.

All the above testing can be done with no display and no keypad.

The minumum components to achieve this are:

Connectors:

• power
• 6 pin programming connector
• USB connector

Other components:

• one Atmega2560 = IC1
• the USB chip - FT245R = IC5
• a 5v regulators (IC2)
• The 24LC512 EEPROM - IC4 - in a socket
• Two electrolytics C33, C11 and C14
• 100nF decoupling C1, C10, C6, C26,C27, C7
• The reset capacitor C19
• The Xtal capacitors (18pF) C15 and C16 .. and the Xtal !
• Resistors:
  - USB - R58, R59 (and R83)
  - I2C pullup R8 and R9
  - FT245R Txd and Rxd pullups R28 and R29
  - Reset pullup R7
• And the two missing earth links - see Glenns web site.

And that's all ...... and the board looks rather empty !

Double click the following images for the high-res version.


TrxAVR-B - minimum config topside. Note that both 5v regulators + caps are installed here (only IC2 needed)
I2C connector installed adjacent to 24LC512 EEPROM.

TrxAVR-B mimimum configuration - bottom side. - note: SMD Xtal used here

Minimum configuration driving TftAVR and a Truly 480x272 4.5inch display

TrxAVR-Picastar home page