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Turns Four! A couple of months ago, we featured an advert for the new PICKIT 4 in-circuit programmer and debugger from Microchip. We’ve long been a fan of the PICKIT and finally, we got our hands on a “4”. What did we think of it? Well, here’s a clue: it’s not going to be sent back in a hurry . . . T he first thing I noticed upon unpacking it is that the PICKIT 4 is slightly wider and thicker than the PICKIT 3. It has an 8-pin in-circuit serial programming (ICSP) header instead of a 6-pin header like the previous version and strangely, I couldn’t see any buttons or indicator LEDs adorning the device (but I figured out where they are hidden later, as you will soon read). On the side of the unit, there is a MicroSD card slot, presumably for programmer-to-go function. This allows you to reprogram a PIC when you don’t have a computer at hand. I also noticed that the USB socket has changed from the mini socket on the PICKIT 3 to a micro socket on the PICKIT 4. What you get in the box Besides the unit itself, there’s nothing else in the box except for a USB Type-A to micro-B cable (around 1.2m long) and a small sheet of PICKIT 4-themed stickers. The back of the PICKIT 4 has a “Get Started” URL listed (microchip.com/ pickit4). Interestingly, the logo on the PICKIT 4 boasts that it is an in-circuit debugger; I hope it can program PICs too! I opened up the web page mentioned and found a product page with a list of specifications and features. Of particular interest to me is the “silicon clocking speed match” feature, which allows it to automatically select the highest possible programming speed for a given PIC. The same page also states that the PICKIT 4 supports the JTAG and Serial Wire Debug protocols. The Quick Start Guide (which can be downloaded from the aforementioned product page) indicates that the two extra pins on the connector are used in JTAG, Serial Wire Debug, UART CDC and SPI modes. This suggests that the PICKIT 4 may be able to provide serial communications while connected to a PIC; something that the PICKIT 3 did not support. The PICKIT 4 can “Hands on” review by Tim Blythman supply power to the target device from the USB host; the voltage is adjustable to suit different PICs. It can also program chips running off their own power supply. When used in “programmer-on-thego” mode, the PICKIT 4 must be powered from a USB power source such as a battery bank. The instructions mention the future possibility the device being powered from the target board but that will require a firmware update. As expected, the microSD card is used to load the firmware in this mode. You press on the PICKIT 4 logo to initiate programming in this mode. Is it a magic logo, perhaps? No, the logo conceals a tactile switch, which has a distinctive action when pressed. Software and setup The MPLAB X IDE/IPE software (version 4.15 or later) is needed to use the PICKIT 4. Since we already had that software installed on our Windows 10 PC (Windows 7/8, macOS and Linux are also supported), we simply we plugged it into our PC to try it out. Once plugged in, it becomes obvious that the indicator LEDs are hidden. Just like the switch, the indicator LEDs shine through Inside the PICKIT 4, shown here about twice life size. The clear triangle you can see left and centre is a LED bar light guide which replaces individual LEDs on the front panel. 90 Silicon Chip Australia’s electronics magazine siliconchip.com.au a light guide, with a purple stripe appearing above the logo, which soon turns blue. At the time of this review, we were working on the Super Digital Sound Effects Module, for which we were using a PICKIT 3. We swapped it out for the new PICKIT 4 and selected the new programmer for the project. Programming the device for the first time involves updating the PICKIT’s firmware to suit the type of PIC being programmed, so we let that happen. Interestingly, the console output for the firmware upgrade notes that the FPGA version is ff.ff.ff. Does it have an FPGA or can it program FPGA’s? We’ll have a look when we open it up later. Some users report that the PICKIT 4 stores multiple firmwares onboard, so the tedious process of the PICKIT 3 slowly updating its firmware when changing between target microcontrollers should be a thing of the past. In use Programming a chip with the PICK4 is noticeably faster than with the PICKIT 3; it took about 1.5s to erase and program the PIC32 in our Sound Effects Module, compared to around eight seconds for the PICKIT 3. Having said that, the IDE software (written in Java) still spends another six seconds connecting to the programmer and checking its firmware before it will initiate programming. The LED stripe on the unit turns green while programming. Like the PICKIT 3, the PICKIT 4 is also capable of in-circuit debugging (see explanatory panel) but the new version makes this much snappier. The older unit took a few seconds to resume from a breakpoint while the PICKIT 4 takes half a second or less. This is one of the biggest improvements to our day-to-day use of this tool, especially since we can now step over a few instructions quickly without setting extra breakpoints. We also found that the PICKIT 4 is able to set breakpoints practically instantly, while the target is running (although the target software appears to pause briefly). This is great for bringing debugging closer to a real-time experience. Interestingly, there’s a speed option (under Program Options/Program Speed) that by default is set to “norIT siliconchip.com.au Comparison between PICKIT 4, at 90 x 43 x 19mm and the PICKIT 3, 95 x 40 x 11mm. The other obvious difference between the two is the apparent lack of LEDs and pushbuttons on the PICKIT 4 – the blue bar on the 4 actually changes colour in use, while pressing the logo triggers a tactile switch. What’s inside? The big news is that the latest and greatest PIC programmer is not powered by a PIC microcontroller, but in fact a 32-bit 300MHz Atmel SAM E70. The internal ISP header looks like the standard AVR 10-pin variant. Of course, Microchip has owned Atmel for two years, so it’s not surprising they would pick the best of both worlds. That’s not the only IC, as there appears to be around fourteen ‘large’ ICs, plus numerous smaller ones around the board, and nineteen test points. Based on this circuit’s complexity compared to the PICkit3, it looks like this PICkit might be a bit harder for the cloners to replicate. The PICKIT 4 appears to be a close relative of the ICD4 In-Circuit Debugger, which also sports a SAM E70 and an FPGA for ‘faster communication, downloads and debugging’, so it appears the FPGA forms part of the high speed USB interface for these parts. There’s an MCP4452 quad I2C digital potentiometer near the ICSP header, presumably used for VPP voltage control, and two MIC2042 power switch IC’s on board. These are rated at 3A, so may be used for VPP generation. There’s another digital potentiometer and a number of op-amps around the board. The IO pins of the ICSP header have substantial networks surrounding them, suggesting a high degree of protection. The light pipe covers much of the board, and appears to be held in place by what looks like a flexible flat cable connector, but is actually an RGB LED module, pointed into the light pipe. The back of the PCB where the pushbutton is mounted has case support preventing the PCB from flexing excessively. Still, pushing the button requires flexing the front of the case and seems like it takes more force than necessary. Next to the USB socket is a small hole in the case which corresponds to a small edge mounted tactile switch marked SW2 on the PCB, which apparently puts the SAM E70 into bootloader mode, after which you should use the ‘Hardware Tool Emergency Boot Firmware Recovery’ from the Debug menu in MPLAB X. We wouldn’t recommend pushing this button for the sake of seeing what it does, but if the PICKIT 4 isn’t recognised by your computer (even after rebooting and or replugging the PICkit), then it may be an option. The PICKIT 4 packs a lot more in than it appears to need, hence the slightly larger case, but with pending support for many more features, possibly including JTAG and AVR ISP and a pleasing increase in speed, it is certainly welcome. The two sides of the PICKIT 4 PCB, removed from its case and with the LED bar indicator removed for clarity (it sits in the angled white socket on the photo above. Other connectors of note are the large I/O socket on the left and the USB socket (right side top photo). Australia’s electronics magazine September 2018  91 The ‘Program Options’ section of the PICKIT 4 configuration has many more options than that for the PICKIT 3. In case it is too bright, the LED brightness can be adjusted (with a range of 1 to 10, defaulting to 5), and the PGC and PGD resistor values can be customised. mal” but can also be set to “high” or “low”. So if the already faster experience isn’t good enough, there’s an even faster option. Some teething problems One small problem we discovered is that the Hold in Reset/Release from Reset option in the MPLAB X IDE no longer works. We found that we needed to disconnect the VPP line between the PICKIT 4 and the target circuit to allow the circuit’s MCLR pullup to get the target out of reset. 92 Silicon Chip Apparently, this is a software bug which has been rectified in MPLAB X v4.20. So if you purchase a PICKIT 4, you should make sure to upgrade to the latest version of MPLAB X to avoid this sort of bug. We also found that we occasionally would get a “Connection Failed” message during programming but this was usually overcome by unplugging and replugging the USB cable from the computer. We have seen similar behaviour from the PICKIT 3 in the past. It may be due to the relatively high power demand of the unit when it’s also powering the target circuit. Interestingly, the PICKIT 4’s LED remains lit when the cable USB is disconnected. It appears the “power programmer from target” setting is active by default, causing the PICKIT 4 to draw power from the target when it has no USB supply. From the notes in the quick start guide and links, it’s apparent the current version of the firmware (supplied with MPLAB) is not quite complete. For example, the Programmer-To-Go support is currently listed as “Feature will be added with a firmware upgrade”. The Microchip forums suggest that this will be added in the August release of MPLAB X. See: siliconchip.com.au/link/aakx The Microchip website also has the following comment: “Currently, the MPLAB PICkit 4 InCircuit Debugger/Programmer supports many but not all PIC MCUs and dsPIC DSCs, but is being continually upgraded to add support for new devices.” With this being the first release of a Comparison of PICKIT family PICKIT 1 Release 2003 ICSP Header No UART tool No Programmer-To-Go No Programmer-To-Go Storage Main Controller IC PIC16C Interface USB Clones available - PICKIT 2 2005 6 pin Yes Yes (128kB) EEPROM (upgradeable) PIC18F USB High Speed Yes PICKIT 3 2009 6 pin No Yes (512kB) EEPROM PICKIT 4 2018 8 pin Yes* Yes* Micro SD Card PIC24 USB High Speed Yes SAM E70 USB High Speed - * some features of PICKIT 4 are not currently available, but are planned for future firmware updates Australia’s electronics magazine siliconchip.com.au In-circuit debugging One of the biggest advantages of using micros from Microchip is the near-universal support for in-circuit debugging (ICD). If you have had to debug a complex program running on a microcontroller with only a serial console (or in some cases, not only that) you will know how frustrating it is to not know what is going on inside the program. You end up having to add a lot of extra print statements, temporarily remove sections of code and constantly re-flash the microcontroller until you can figure out what’s going wrong. All of that pain can be avoided by using incircuit debugging. The main thing you need to do so that you can use this feature is to ensure that the programming pins do not share their functions with any other hardware that may interfere with the debugging signals. You also need to compile the project in debug mode, which normally uses less aggressive speed/size optimisations. Once you have done that, you can set “breakpoints” on just about any line in your software and when you start the debugging session, the program on the PIC will run until it reaches one of these breakpoints. It will then stop and the code surrounding that line will be shown on the screen (see screen grab below). You then have the ability to perform the following actions: • Inspect the state of all the variables at this point in the execution of the program. That includes global variables and those local to the function containing the breakpoint. • View the “call stack” which shows you which line of which function called the cur- rent function and so on, up to the entry point function (normally “main”). • Inspect the state of the PIC’s RAM, its control registers and so on. Basically, you have full access to a snapshot of the PIC’s state at that point in the code’s execution. • “Step” through the code one line at a time and see which order the statements are processed (which will depend on any loops, if statements, function calls etc which are encountered). • See how variables and other processor state changes as the program progresses. In fact, variables, registers or memory that you are “watching” will be highlighted in a different colour when the state changes for any given step. • Change breakpoint locations, including deleting existing breakpoints or setting new ones, and then allowing the code to continue execution until it encounters another breakpoint. In fact, one valuable aspect of in-circuit debugging is the ability to set a breakpoint and see whether the code on that line is ever reached. This should give you an idea of how much easier it is to diagnose and fix complex faults in the software using ICD compared to other techniques. The fact that the PICKIT 4 makes it faster is a great benefit. It’s difficult to use ICD to diagnose timingsensitive problems as debug mode changes program timings and any time the program is frozen (eg, when encountering a breakpoint), real-time tasks running in the processor also halt. But it can still be useful in some of these situations. PICkit since the merger of Microchip and Atmel and with the extra pins on the ICSP header, users will be curious as to whether it can program Atmel parts such as AVRs. This too appears to be a future capability, with support still to be added to MPLAB X. Interestingly, the 8-bit AVR family appears to be available as an option in both the current IDE and IPE, although no actual parts are available for selection. Conclusion As far as we’re concerned, the PICkit 4 does what we need it to do, ie, it programs and debugs PICs, and it does both much faster than the PICkit 3 did. So we feel that the hardware improvements makes the cost of upgrading well worthwhile. If you’re hoping to program AVRs or use the programmer-to-go function, you may want to wait until the software is ready to pull the trigger. You should also check that the PICkit 4 has software support for the PICs you intend to use, in the latest version of the MPLAB X software. so, check which version of MPLAB X SC you’ll need. MaxiMite miniMaximite or MicroMite Which one do you want? They’re the beginner’s computers that the experts love, because they’re so versatile! And they’ve started a cult following around the world from Afghanistan to Zanzibar! Very low cost, easy to program, easy to use – the Maximite, miniMaximite and the Micromite are the perfect D-I-Y computers for every level. Read the articles – and you’ll be convinced . . . You’ll find the articles at: siliconchip.com.au/project/mite The in-circuit debugger being used on the Super Digital Sound Effects Module. Three breakpoints have been set. The code is paused on the second breakpoint and the bottom window (“Watches”) shows the value of monitored variables. siliconchip.com.au Australia’s electronics magazine Maximite: Mar, Apr, May 2011 miniMaximite: Nov 2011 Colour MaxiMite: Sept, Oct 2012 MicroMite: May, Jun, Aug 2014 plus loads of Circuit Notebook ideas! PCBs & Micros available from PartShop September 2018  93