Juma TRX-2 Version 2.00

Software developed by Adrian

Juma TRX-2 Version 2.00

Postby 5B4AIY » 04 Aug 2015 11:54

Version 2.00a changes the way that the EEPROM checksum is calculated and verified.

NOTE: Because this version uses a different algorithm to calculate the checksum there will be a checksum error message on initial boot after loading this firmware. This will force the default calibration and configuration data to be loaded. Please make a note of your existing calibration and configuration settings before loading. There are pages at the rear of the User Manual specifically intended for this data.

In all previous versions of the firmware a simple sum and complement scheme was used, and, whilst in the four years I have been making these modifications and responding to user requests I have not had a report of a failure of this, it has always concerned me that only the most gross EEPROM errors would be detected.

For example, suppose you had only two bytes to checksum, and the result was 5, using the summing method you cannot detect whether this is as a result of 5+0, 4+1, 3+2, 2+3, 1+4, or 0+5. The more data you wish to check, the greater the possibility of error.

A Cyclic Redundancy Check-code however would give 6 completely different checksums for these values, allowing you to reliably detect even subtle errors. In fact, using the simple 16-bit CRC algorithm I've incorporated in this firmware the results would be: 5+0 = A223, 4+1 = 0222, 3+2 = A1E1, 2+3 = 01E0, 1+4 = A0A3, and 0+5 = 00A2 showing that complimentary errors and transposition errors are detectable.

For a full description of the method, please see the comments associated with the crc_16() function in the file juma-trx2.c

If you are updating from an earlier version of my firmware, then assuming you noted your existing calibration and configuration data first, all that is required is to re-enter your data and perform the auto-equalise procedure. If you are updating from an original firmware, then you will have to re-calibrate as the measurement system is completely different.

Take special note of the fact that in this firmware output power calibration is performed with the attenuator set to 3dB, and therefore the maximum power output when calibrating is 5W - do not exceed this! This was done as explained in an earlier post to both improve the accuracy as well as reduce the thermal stress on the PA.

Equally, there are two different settings for the S-meter calibration depending upon exactly which transistor you have installed at TR4 of the variable gain amplifier A4-B on the main board. Early transceiver kits were supplied with the SST112 FET device, whereas later kits use the PMBFJ112 FET which has a different threshold voltage leading to a different calibration setting.

For further details, please see the System Calibration & Setup section of the User Manual (Page 9).


Adrian, 5B4AIY
Juma TRX-2 v2.00a Build 3 (C-Source+HEX Load File+User Manual).zip
Added EEPROM CRC checksum calculation.
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