Hi All, To the group, for your interest, a dry solder joint on IC U18 MAX 232 at 5 V logic side caused my issue. Although RS-232 data went in, it did not reach CPU. My MAX 232 was badly soldered due to initial assembly had some discoloured IC pins and solder did not free flow. Completely removed IC, cleaned and reflowed. Thanks to those providing comment. Regards, Gerald VK3FGJM
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