Hi all
I updated the?SSB?beta?testing webpage of the brave, here:??and released?firmware?version?1_01_004?to it. I did not solve problems with SSB phase distortion calibration, but I added a couple of additional failsafes. I am inclined to stop calling it beta. But I welcome your opinions on this. I know there is more to do, there will always be more to do... I think I would be more comfortable calling it the official version and moving onward. Having it all properly documented in the operating manual and all in one place would simplify things and reduce confusion. What do you think??
These are the changes:
- Bug fix: Incorrect PA voltage display on the Diagnostics screen due to 57 / 10 being rounded to 5, as discussed in this forum.
- Change TX color in the diagnostics screen from red to blue, to avoid confusion since red things are errors.
- Added two more USB Virtual COM serial ports. QMX now presents itself as a USB hub with a 24-bit stereo 48ksps USB sound card and three USB Virtual COM serial ports attached. The advantage of this is that you can be running WSJT-X connected to a serial port, then run a terminal emulator connected to a different serial port; then you can make adjustments to the gain for example, to get the WSJT-X SNR meter at your desired level. You can also use other tools like "Input analysis" in the "PC and CAT" menu, which displays incoming audio tones from the PC; previously this could not be used unless you used VOX for Tx/Rx control. The CAT monitor can also be useful to be able to monitor incoming CAT commands and responses in realtime?on one port, with CAT running on another. And going forward, for developers who wish to experiment with BASIC scripting, it will also be important to have multiple serial COM ports.
- Added CAT LC; command to retrieve LCD contents: it returns a 32-character string, whose contents are whatever is on the LCD at that instant. Any custom characters are replaced by spaces. The only exception to this is the VFO indicator which is replaced by an 'A' or 'B' character.
- Added CAT commands SA; which returns the AGC dB value (dB of attenuation applied by the AGC system).
- Added CAT command SM; which returns the S-meter value. This value is in dB. To convert to S-units, divide by 6.
- Added CAT command PC; which returns the power level during TX. The value is in tenths of a Watt. For example response PC45; would mean 4.5W.?
- Added CAT command SW; which returns the SWR meter reading during TX. The value is in units of hundredths. For example response SW142; would mean the SWR measured is 1.42.?
- Added CAT command SS to get/set SSB input source. Valid values are 0 (USB from PC), 1 (Two-tone test generator) or 2 (External microphone).?
- I migrated AF, RF, Image, LPF and Test ADC I/Q terminal tools to the standard ASCII-art graphing tool I developed. Previously every tool had its own piece of code, which of course were copy-and-pasted from each other and largely similar. The advantage is also that the standard ASCII-art graphing tool I developed, also has an interface to display a miniature version of the graphs on a 20 x 16-pixel canvas, shown in a 4 x 2 character section at the right-hand side of the LCD. This means all these sweep tools are now also available on the LCD and buttons, without needing to use the terminal emulator to see them. They are all under the "Hardware tests" menu.?
- I created a new tool called "PA mod. test" specifically to check the operation of amplitude modulator. This is under the "Hardware tests" menu both on the terminal interface and the LCD user interface. Attached is an example of a correctly functioning amplitude modulator. The x-axis shows the DAC value, the y-axis shows the measured PA voltage. A correct result is a straight line that goes (almost) from zero to (almost) the QMX supply voltage; a 12V unit will saturate at about a DAC value of around 2500 as shown.?
- The Hardware tests / Diagnostics screen is now also available on the LCD interface. Here there are 6 screens, which you scroll between by using the Tune knob. You initiate TX (if you wish) by pressing the left button (Keyer/RIT/Menu) button. The six screens are Supply voltage, 3.3V SMPS, 5V SMPS, Bias SMPS, TX and Keyer inputs. When scrolling through these screens, any items which are errors (which on the terminal would be colored RED), on the LCD they flash at a rate of 2.5 Hz to get your attention. You can change the band by turning the Volume knob. So in this way you can easily do all the functions of the Diagnostics screen, on the LCD itself without needing a terminal emulator.?
- The SSB calibration tool now tests the PA amplitude modulator first, and refuses to run if the modulator isn't working properly. To determine if it is working properly or not, it sets the DAC value to 1000. This should produce a PA voltage of around?5.02 V in theory. "Fail" is when the measured voltage is outside the range 4 to 7V. Probably this range is too wide and could be considerably narrowed. But it should easily identify cases where a fault in the amplitude modulation circuit is causing the PA voltage to be always at max.,?which would both prevent proper phase distortion measurements, as well as prevent SSB generation working, as well as stress the PA transistors because they'd run at full power during the entire lengthy calibration process.?
- I have not yet changed or improved the way calibration works; but now if the calibration fails by producing nonsense phase error measurements, and has not got further than DAC value 600, then it is called a "Fail" Calibration now writes zero phase compensation for the entire vector, if that band calibration fails. This way you could continue with other band calibrations, and still have Phase predistortion switched on, it will just have no effect because the phase predistortion?vector will be all zeroes.?
Here is a note about the multiple new USB Virtual COM Serial ports, because it's interesting (well I think so anyway) and I made an interesting discovery.?
Many years ago (2018) when working on the QSX project, Alan M0PUB was very very helpful, he is an expert on USB and on STM32. The ST library examples have various common USB device examples including Virtual COM Serial. But they do not have any examples or any library support for "Compound Device Class", which is what you call it when you have multiple USB devices effective on ONE USB cable. In other words it's like one of those little USB hub things you plug into your PC and it provides 4 separate ports; but in this case, it is all done virtually. So Alan helped out (A LOT) by writing me some code for Compound Device Class support, with a 48ksps stereo 24-bit USB sound card and a USB Virtual COM Serial port as the two devices. This code was written originally to help me with QSX, but it is now in QDX, and in QMX.?
Resource constraints exist on the STM32F446 microcontroller.?
Firstly there are only 6 endpoint pairs numbered 0 to 5. An endpoint is a buffer for USB communication between a host (your PC) and a device (the QMX). A "pair" means that it has one for sending data in one direction from host to device, and one for sending data in the other direction from device to host. Endpoint 0 is always used in USB systems for control purposes. A USB Sound card (USB Audio device) requires 1 endpoint pair for in/out audio streaming. A USB Virtual COM Serial port requires TWO USB endpoints, one is for data in/out and the other is called the "Command" endpoint. So 1 endpoint used for control (endpoint 0 always), 1 endpoint for audio, and 2 endpoints for Serial COM, that means 4 of the 6 are until now, used up.?
The other resource constraint is the 1280 byte FIFO buffer in the microcontroller. The definition of how this buffer is allocated between the various USB endpoints on both send and receive, and is a "little" complex :-/? There are rules in the STM32F446 reference manual about how to allocate the FIFO buffer. But there aren't any warnings if the FIFO isn't allocated correctly, or if it is over-allocated; just nothing will work properly. Alan M0PUB commented way back in 2018 that the 1280 byte buffer, being only 320 32-bit "words", isn't very large at all and is only marginally sufficient in this application because 24-bit stereo 48ksps audio in and out uses up a fair chunk of it (with 1000 USB transactions per second).?
Alan M0PUB's excellent work resulted in a transparent "USB hub" wrapper for the devices, which doesn't use up any endpoints or FIFO space, all of which are dedicated to the end devices themselves (Audio and Serial).?
The issue is only 2 spare endpoint pairs. But I wanted to add at least ONE more COM serial port, as well as be able to add a USB Flash drive in future too, for the BASIC scripting implementation - for the possibility of users being able to share programs, copy them into QMX etc. Since a COM serial port uses up two endpoints, and a USB Flash drive would require one, that would need THREE Spare endpoint pairs, but only TWO are available - even before we start considering the scarcity of the FIFO buffer hardware.?
After a certain amount of research I learned that what is called the "command" endpoint isn't really for commands, it's not a very good name for it. It's for event notifications from the device to the host (unidirectional only), and indeed some implementations call it (a better name, I think) the "interrupt" endpoint. Virtual COM serial is actually only one sub-class of the "Communications Device Class" USB device type. It so happens that some types of serial port like the old RS232 which had not just Data Transmit and Data Receive signals, but also control signals such as request to send (RTS), clear to send (CTS), data terminal ready (DTR), and data set ready (DSR). Use of these is sometimes called "hardware flow control", as opposed to "software flow control" which uses only Transmit/Receive data signals and manages readiness in software.?
QMX uses software flow control and it turns out that in this limited subset of functionality, there is NEVER any need to send event notifications to the USB host. The "command" (really interrupt or event notification) endpoint of the Virtual COM Serial port is therefore entirely wasted as it is never used. What a pity to waste such valuable endpoints, where there are only six available in an STM32F446, on event notifications which are NEVER needed in our application! And how unfortunate tending toward TRAGIC that much lesser STM32 microcontrollers in the family, such as the STM32F103 used in the U4B, and the STM32F070 used in the ProgRock2, have EIGHT bidirectional endpoints not 6.?
But I discovered an interesting solution experimentally! The "command" or "interrupt" endpoint of each Virtual COM serial port can be defined as a non-existent endpoint, not a real one, and allocated no FIFO buffer space. So in this beta version of QMX firmware, there are three Virtual COM serial ports. You will find them for example as COM4, COM5, COM6 in a Windows system (perhaps), or as /dev/ttyACM0, /dev/ttyACM1 and /dev/ttyACM2 in a Linux system (unless there are other ttyACM USB devices on the PC, in which case they could be numbered 1, 2, 3 for example).
The data in/out endpoints are assigned to actual endpoints in the microcontroller numbered 2, 3 and 4 (remember 0 is for control, and 1 is for the Audio USB soundcard). The corresponding command/interrupt endpoints are unidirectional from device (QMX) to host (your PC) and are assigned to non-existent "ghost" endpoints 6, 7 and 8. The fact that these endpoints don't really exist doesn't matter for QMX, because it is never ever going to send any data over them. The PC is also happy, because according to its theories, a USB Virtual COM port should provide two endpoints, one for bidirectionally for data and one unidirectionally for "event" notifications; the PC doesn't know that the endpoint at the other end of the link doesn't really exist and that it will never receive any events on it.?
Everyone's happy, both PC and QMX; and the QMX now has THREE serial ports, as well as still a spare endpoint I can use for a USB Flash drive. It proved possible to fine-tune the FIFO use so it works also. I'll stop waffling now but it was an interesting exercise to me.?
