TrxAVR_Picastar - Port diagnostics

The hardware port diagnostics provision consists of:

• A Window in Hobcat to drive the ATmega2560 ports as outputs or to read then as inputs.
  This works via USB and so cannot deal with USB control lines: PORTD 2-6.
• A small program to cycle the bits of PORTC and PORTD as outputs. This is intended to be used if USB if not working.

First a quick summary of the stages/levels in getting trxAVR-Picastar up and running.
(See setup instructions for more detail)

• With power on the board and TrxAVR neither programmed nor running, the PC can identify the FT245R USB chip
  and Mprog will connect to it via USB to configure it.
• When the FT245R USB chip has been configured (ie with the letters TRXAVR within its id string), then the Hobcat status
  bar will show its id information.
• When the ATmega2560's fuses are set and it has been programmed with trxavr.hex, then Hobcat's status bar will report
  TrxAVR v n.nn ready. .. and the debug window will operate and display Atmega2560 ports and variables.

If all this doesn't happen - then there may be a hardware fault and the hardware diagnostics may useful.

The following are important in diagnosing hardware faults:

• The FT245R USB uses ATmega2560 PORTC as a bidirectional databus and PORTD bits 2-6 as control lines.
• PORTC is mulitplexed between FT245R, display data (also bidirectional) and keypad matrix drive.

We have two situations:

1. USB working - so we can use the USB link to look at the ports except Port D bit 2-6
   - yes we can look at PORTC via USB (It is momentarilty taken over for USB data and then released back to our testing.)
2. USB not working. This where the separate tiny application TestPortsCD.hex can be used to check out ports C and D
   which are used by USB and may have a problem.

USB working - Hobcat's PortDiagnostic window.

This is called from Menu | Tools | TrxAVR port diagnostic and is shown below:
(Note: this window will not be active until DSP load is completed (very brief if no DSP code loaded yet!)

The window displays all bits of all ports except PORT D bits 2 - 6 which are FT245R USB control signals.
It can be be used in Read or in Write mode:

• In write mode it sets all ports as outputs (DDRn = 0xFF) and the check boxes define which bits are set (ie +5v).
  All the ports are transferred from display to TrxAVR whenever a checkbox is checked or unchecked or when the
  Write button is clicked.
• In read mode, all the ports are made inputs (DDRx = 0x00). The input states (PINx) are read into the display
  whenever the Read button is clicked.

The first Read or Write action, as above will put TrxAVR-Picastar in diagnostic mode. A rig reboot is thereafter required to
restore normal operation.

Serial and encoder interrupts are disabled, internal timers are disabled and the analogue inputs become digital I/O.

PORT C is used for USB data but only momentarily. On Read mode, the 1k serial input resistors prevent the applied
logic level from interfering with FT245R-Atmega2560 communication. (But dont connect inputs direct to the port!)

USB not working

TestPortsCD.hex is program which simply sets PORTC andPORTD as outputs (DDRC=0xFF, DDRD=0xFF)
and cycles the output states. TestPortsCD.hex is loaded using the programmer (ie: AVRISP2, Ponyprog)

Each half of PORTC and PORTD behaves as a 4 bit counter at 0.5Hz. (ie counts 0 - 15 repeatedly)
Short circuits are likely between adjacent pins and so the main requirement was that adjacent pins shoul have different
signal patterns.

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