Note - This only applies to using Manual CW (Straight Key Mode or Iambic Mode) with sBitx Version 3.052.?? This recap includes some previously shared information.

Goal

Make my zBITX with sBitx version 3.052 firmware usable for Manual Straight Key CW Mode and Manual Iambic Paddle CW Mode.? At any speed.

Problem

A script starts the underlying sBitx program in a new virtual shell.? Anything that the version 3.052 sBitx program writes out to the console (stdio) is written to this new virtual shell.?Whenever using Manual CW, programs (mostly i2cbb.c) are madly writing error messages to this virtual shell on every Key Down event and every Key Up event.? This virtual shell keeps growing and growing until it eventually consumes all available real memory and all swap space.? Whenever that happens, the sBitx program becomes totally unresponsive.? From the outside, it looks like the zBITX has crashed.

Cause

The main RasPi Zero computer running the sBitx program talks to the RasPi Pico computer running the zBITX’s LCD Display using the I2C protocol.

Due to the way that Manual CW is now being handled in sBitx version 3.052, the ic2bb.c program that is managing I2C communications is now writing out error messages whenever (1) it wants to get control of the I2C bus, but cannot because the I2C bus is already busy, and (2) it gets so backed up with the volume of incoming requests for the I2C bus that it aborts and reconnects. ?The sBitx version 3.052 sbitx_gtk.c program is also writing out I2C related status messages.?

So why now in version 3.052 and not in version 3.021?? The ic2bb.c program was not changed.? The root cause was adding in the Interrupts (IRQs) for the manual CW Mode in version 3.052.? ?I see two things that cause the i2Cbb.c functions to become overwhelmed: ?These IRQs are now being generated on both a 'Key Contact Closed' and 'Key Contact Open' (the downstream CW processing requires both events). And the IRQ processing function is not debouncing the Key Contact Closed event or the Key Contact Opened event.? ?What you may think is one Contact Closure generating one Interrupt, is really one Contact Closure generating tens of Interrupts.

?Solution

A ‘Partial Solution’ was achieved by modifying the i2cbb.c and the sbitx_gtk.c files to comment out all of these I2C related Debug and Status Messages that were being written out.?? This eliminated the ever-growing virtual console problem that was bringing down the zBITX whenever using Manual CW.

The ‘Real Solution’ is to debounce the 'Key Contact Closed' and 'Key Contact Open' inputs to minimize the large number of redundant messages that are going to the i2cbb.c I2C handler. ?My ‘Partial Solution’ only gets rid of the subsequent Error Messages and Status Messages.? The i2cbb.c program is still being bombarded with a large number of redundant messages, and it still has the same resource contention, connection aborts, and reconnections. ?While the zBITX device continues to run while this is happening, you will see jitter and delayed information being displayed on the LCD display.

Result

I had no problems implementing the ‘Partial Solution’.? The files needed to do that for sBitx version 3.052 are available below.

However, I have thrown in the towel on implementing the ‘Real Solution’.? Over the last several days, I have tried many different approaches to debounce both the 'Key Contact Closed' and the 'Key Contact Open' events.? RasPi OS interrupt handlers, microsecond timers, and fprint() debug messages don’t seem to play nice with each other.? Nothing that I tried would catch and debounce a 'Key Contact Open' event right after a debounced 'Key Contact Closed' event.?? Not saying it cannot be done – just saying I am tired of spending my time seeking a way to achieve this. ??Sorry.

Going Forward

You have a few choices:

If you are using Manual CW (Straight Key or Iambic) with your sBitx version 3.052 system, and you are willing to remove power and reapply power every 30 minutes or so, you may continue on with what you have.

If you are using Manual CW (Straight Key or Iambic) with your sBitx version 3.052 system, and you are able to install my revised files, then you can use my ‘Partial Solution’.? Save your existing /home/pi/sbitx/ic2bb.c and /home/pi/sbitx/sbitx_gtk.c files to a safe place.? Put my revised i2cbb.c and sbitx_gtk,c files into you /home/pi/sbitx subdirectory.? Then while in /home/pi/sbitx, ?execute ?./build ???Then remove power and reapply power.? As far as I know, this will let you use Manual CW, at any speed, for many hours.

If you are using Manual CW (Straight Key or Iambic) with your sBitx version 3.052 system, you may wait for Ahhan to provide a new zBITX firmware release that fixes this problem of Manual CW operation consuming all available memory and all swap memory.

Caveat

This is not an official zBITX release.? I am not setup for using SSB, AM, FT8, or any other mode with my zBITX.? ?While I do not see where my changes to this i2cbb.c file and this sbitx_gtk.c file to make Manual CW usable will have any impact on these other modes, I have not tested any other mode.

72,

Jody – K3JZD