If the SUP> prompt does not appear after a maximum of 20-25 seconds, that means there's something wrong. That doesn't mean your RPi0 is not working; especially if you saw the flashing green LED light on it earlier. This more than likely means that you didn't transfer the NextPI2 image properly or that there's some problem with the microSD card you used.

To verify the RPi0 is working, you will need to unplug it from your ZX Spectrum Next, locate a micro usb power supply, an appropriate HDMI™ cable and a standard RPi0 distribution and power it independently.

If you can see output on the screen, then there's either a problem with your NextPI2 SD card (which you can verify by plugging its microSD card in the RPi0's reader instead of the standard RPi0 distribution), a cold solder on your IDC connector you soldered earlier, or finally, an insufficiently powerful, power supply for your ZX Spectrum Next.

The RPi0s are very resilient pieces of hardware and they don't fail easily; chances are any failure you experience is due to one of the cases listed.

Using the Real Time Clock hardware

If you're lucky to have an expanded ZX Spectrum Next with the battery backed-up Real Time Clock (RTC) hardware installed (or if you followed the instructions to install it yourselves) then more options in timekeeping become available to you. These options do not suffer from the drawbacks and caveats laid out in the previous sections as this dedicated hardware option keeps time regardless of what else the computer is doing and in fact keeps time even when the computer is turned off.

The RTC is accessible via the function TIME$ (See Chapter 17) as well as two dot commands: .date and .time.

Setting up your RTC for first use

As we saw above, invoking the Set Clock option found in the Tools submenu of the NextZXOS Startup Menu has the obvious benefit of setting up the clock AND testing at the same time. There are however two more ways to set your RTC up, especially if for some reason you wish to use an alternative to NextZXOS like for example esxDOS.

Using .time and .date

This is very straightforward with the small exception that before you can use .date and .time you will need to set up your Real Time Clock hardware. Luckily this is only done once when you install it and whenever you need to change battery. You will initially (for safety) need to issue the command:

.time -di

This wipes the RTC signature from the chip and gets it ready to accept a date and time. You can then type:

.time "10:35:23"

where "10:35:23" can be substituted by any string of the format HH:MM:SS where HH (hour) is a number from 00 to 23 , MM (minute) is a number from 00 to 59 and SS (second) is a number from 00 to 59. You then enter the correct date by issuing:

.date "20/03/2023"

where "20/03/2023" can be substituted by any string of the format DD/MM/YYYY where DD is the day (01 to 31), MM is the month (01 to 12) and YYYY is any year from 2000 to 2099.

A few interesting things will happen once you install and setup your RTC. First, NextZXOS will report the time and date on its Startup menu (which is very nice indeed). Then, your saved files will start having a date and timestamp on them (visible with CAT EXP or .ls).