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Constructional Project How to program SMD microcontrollers with TQFP Programming Adaptors Our new PIC Programming Adaptor, described last month, can program many chips in DIP, SOIC, MSOP, SSOP and TSSOP packages. But SMD micros come in other packages, including SOT-23-6 and QFPs (quad flat packs). This article explains how to program such devices out-of-circuit with several reconfigurable programming jigs. By Nicholas Vinen T hese jigs are inexpensive and straightforward to make. Still, they are invaluable if you need to program SOT-23-6 or QFP microcontrollers before being soldered to a board, such as when the board lacks a programming header. They aren’t limited to PICs; they will work with most microcontrollers in these packages, including AVRs and many ARMbased types. We use jigs like these all the time to program chips we sell, including the ones below: ● The 64-pin PIC32MX470F­ 512H-120/PT programmed for the Micromite Plus (Explore 64). ● The 100-pin PIC32MX470F­ 512L-120/PF, also for the Micromite Plus (Explore 100). ● The 44-pin PIC16F18877-E/PT for our recent Wideband Fuel Mixture Display (WFMD). ● The 32-pin ATSAML10E16A-AUT for the High-Current Battery Balancer. Those are all QFP chips but with different numbers of pins, so a separate jig is needed for each one. Note that sometimes QFP chips with the same number of pins can be different sizes, so you may need more than one jig with the same pin count. However, as our jigs are reconfigurable, you only need one of each, even if you need to program different chip types in that package. Most QFP micros actually come in either TQFP (“T” stands for “thin”) or LQFP (“low-profile”) packages. The sockets we’re specifying suit TQFP, although other types may be available. Let’s go through the jigs individually, from the fewest pins to the most. SOT-23-6 This suits tiny PICs like the PIC10(L) F202-I/OT or PIC10(L)F322-I/OT that we used in our Remote Control Range Extender (January 2023). These often need to be programmed out-of-circuit because they’re typically used on very small PCBs that probably don’t have much room for a programming header. This is the simplest jig as it is just made of a commercial SMD to DIP adaptor (AliExpress pemag.au/link/ abmu) plus five female-to-male jumper leads. It is shown in Photo 1, and the wiring is shown in Fig.1. Fig.1: here’s how to wire a PICkit 4 to an SOT-23 programming socket via jumper wires. It might not look ‘kosher’ but we’ve found it works fine, even without local supply bypassing for the PIC being programmed. Photo 1: the SOT-23-6 ‘test socket’ can be wired to a PICkit 4 using five male-female jumper leads. Then tape or glue them together where they go into the PICkit. This work fine despite the lack of bypass caps (the software verifies the programming so it would catch any errors). 28 Practical Electronics | October | 2024 SMD Programming Adaptors Fig.2: our four TQFP programming adaptors all follow this basic configuration, designed for maximum flexibility. The headers around the socket make it easy to connect any pin to GND, Vcc, Vdd or one of the pins on the programming header (CON35/CON36) via jumper wires. The optional regulators at the top can derive two different Vdd & Vcc supply rails from an external DC source. Practical Electronics | October | 2024 29 Constructional Project While there are no bypass capacitors or anything like that, we’ve found it works fine as long as the jumper leads are kept short. If you come across a different micro in the same package that uses a different pinout, rearranging the jumper wires to suit will be simple. The socket is pretty expensive at about £30, including delivery, but it works well, and there aren’t many better options. If you only need to use it occasionally, a cheaper option is to design a PCB with an SOT-23-6 footprint wired to a programming header. Then, instead of soldering the chip to its footprint, simply hold it in place with a clothes peg or similar. That can work surprisingly well, but it’s fiddly. We would only do that for the occasional chip; we wouldn’t want to program dozens that way. TQFP-32, -44, -48 & -64 We have two options for TQFP package chips. The first is the simplest but only suits chips like the ATmega328P. They are so common that you can get an adaptor that converts the pinout to the through-hole (DIP-28) equivalent. For example, this one costs £10, including delivery, at the time of writing: pemag.au/link/abmv Fig.3: how the 32-pin TQFP programming adaptor rig would look if you fit all the components. That would give you all the options you need for programming any chip in this package, but in most cases, you can save yourself a bit of time and a few dollars by only adding the components you need for programming a given micro. Fig.4: this shows how we built a very minimal programmer for the ATSAML10E16AAUT ARM-based microcontroller from Atmel (now Microchip) on the same PCB shown in Fig.3. That chip is programmed using the AVR SWD (serial wire debugging) protocol, which uses different pins on the PICkit 4 8-pin header compared to PIC programming. 30 Say you have a means of programming a DIP ATmega328P, such as a TL866II or the newer T48 universal programmer. In that case, you just need to purchase the SMD adaptor, slot it into that programmer and away you go – see Photo 2. A more flexible option that also works with chips like the ARM-based ATSAML10E16A mentioned above is our custom adaptor board that accepts a commercial TQFP programming/test socket. Its circuit is shown in Fig.2 and the matching PCB overlay in Fig.3. There are relatively few components on it, so it’s pretty easy and inexpensive to build. Our larger 44-pin, 48-pin and 64-pin adaptors follow the same pattern, so the following description will cover all of those. PCBs for all four versions are available from the S ilicon C hip Online Shop. The test sockets are well made, have gold-plated contacts for a long life and only cost about £8-13 each. We have links to each one we’ve tested in the parts list. They have a staggered pin pattern unsuitable for use with protoboard and such, hence our custom PCB designs. Each PCB suits a specific socket. Surrounding that socket, we have six rows of headers with one pin for each socket pin. The three closest to the socket allow you to use a jumper to connect that pin to GND or one of two power supply rails. You can also plug in a female header upside-down that lets you connect a capacitor from that pin to GND, or a capacitor to GND plus a connection to the supply rail. For pins used for programming, it’s a simple matter of fitting a short female-female jumper lead between the pin in the middle row and one of the ICSP header pins. Two sets of headers are provided to make it easy to connect these pins to an ICSP dongle like a PICkit or Snap programmer (PICkits can program AVRs now too). The second set of three headers allows you to choose, for those pins connected to a power rail, which power rail that is. That is done by placing a jumper between the centre pin and either the Vcc or Vdd row. Note that most micros don’t need two rails for programming, so you can use Vdd exclusively for those, but we wanted to provide maximum flexibility. Each set of Vcc and Vdd pins along each side of the chip has a pair of Practical Electronics | October | 2024 SMD Programming Adaptors Photo 2: this socket comes pre-mounted on a small PCB with a pair of SIL headers on the underside. They are routed to match up the pinout of the TQFP-32 version of the ATmega328 (and similar chips) to the DIP-28 version, so a standard DIP programer can be ◀ used to program the TQFP chips. bypass capacitors to GND. This means you can get away without needing to add bypass capacitors closer to the chip in most cases; you can simply use jumpers to connect GND and Vdd where required. Two adjustable or fixed linear regulators can be mounted in the board’s upper left and upper right corners to supply either the Vcc or Vdd rail. In most cases, we use a PICkit to deliver power to Vdd via its header and don’t bother with these. But again, this gives you flexibility. Using these regulators, you could derive Vcc and/ or Vdd from USB 5V, a plugpack or a bench supply. Pads are also provided to fit SMD LEDs to show when the Vcc and Vdd rails are powered. Finally, there are rows of pairs of uncommitted pins that you can use for jumpering signals if required. The only connections on the board are between the pairs of pins. Fig.4 shows the minimal parts needed to configure this board for programming the ATSAML10E16A, while Photo 3 shows our actual jig. That demonstrates that you only need to fit the parts you need for a particular application, and you can add more Practical Electronics | October | 2024 later if necessary. Here, we’re using the PICkit 4 in its CORTEX SWD mode (it also supports AVR ISP, among other protocols). One thing to note about these jigs is that the space around the socket is tight. That’s because we’ve broken out the pins close to it, keeping the track lengths as short as possible. It’s a little squashed, but we’ve programmed hun- ◀ Photo 3: a minimalist assembly of the 32-pin TQFP adaptor set up for the chip stated on the label. Labelling the adaptors so you can remember what chips they are set up for is a good idea. dreds (if not thousands) of chips with these jigs and haven’t had any real difficulty getting them in or out. However, that could be a good reason to avoid fitting parts you don’t think you’ll need. There are mounting holes in the corners for tapped spacers, so the jig sits flat on a bench. That makes them much easier to work with. Fig.5: here’s where all the components go on the 44-pin TQFP programming adaptor. This package is pretty common for 8-bit PICs (eg, PIC16F18857 and PIC16F18877), 16-bit PICs (eg, dsPIC33FJ128GP804), 32-bit PICs (eg, PIC32MX170F256D-I/PT) and AVRs (eg, ATmega644PA). 31 Constructional Project Fig.6: this shows how we wired up our assembled 44-pin TQFP programming jig to suit PIC16F18877-I/ PT chips. Target power is delivered by the PICkit. The programming connections go via the pins on the “Pwr” row and then via jumpers to the IC pins to keep them away from the front socket opening. Fig.7: here’s where the components go for the 48-pin TQFP Programming Adaptor. We have the parts to build one but haven’t done so yet because micros in this package are far less common than either 44 pins or 64 pins. We have placed a large filled circle on the PCB silkscreen at the upper-left corner of each TQFP socket to indicate where pin 1 of the IC would typically go. You then line up the dot or divot on the chip with that marking. All that means is that the pin number labelling on the headers will be correct when the chip is orientated like that. You could use a different orientation and reroute the connections to suit if you wanted to, as there are no fixed connections to the socket on the board. Still, keeping pin 1 in the upper lefthand corner is less confusing. 32 TQFP-44 programming rig We haven’t drawn the circuit for this one as it’s the same as Fig.2 but expanded for the extra pins. The PCB overlay is shown in Fig.5. Photo 4 shows our jig, currently configured for the PIC16F18877-I/PT, while Fig.6 shows that wiring. Other chips we’ve programmed with this rig include the PIC32MX170F256D-I/PT and ATmega644PA. Note in Photo 4 how we’ve plugged a 3-pin socket into the header for pin 28 (Vdd) with a capacitor soldered across one pair of pins and a short wire across Photo 5: the 64-pin TQFP Adaptor board set up for a PIC32MX470. If you don’t need to make connections to the pins on the top row of the socket, especially in the middle, it can pay to leave those headers off, as it might allow you to open the socket clamshell wider, making it easier to get chips in and out. the others. It acts as a jumper to connect Vdd to that pin while providing a bypass capacitor to GND. TQFP-48 programming rig Again, the circuit is the same as Fig.2 but with extra pins on the socket, while the PCB overlay is shown in Fig.7. We haven’t built one yet as we don’t need it. That’s because most microcontrollers in 48-pin TQFP packages are ARM-based types that we haven’t used (from Infineon, Renesas or Silicon Labs). Still, we designed the board and Practical Electronics | October | 2024 SMD Programming Adaptors Photo 4: here, we have installed all the headers around the 44-pin TQFP socket to make the Adaptor more flexible. Note the addition of a bypass cap on one of the supply pins using an upside-down three-pin socket. A closeup of the ‘jumper’ made out of a 3-pin socket and capacitor we had to make is shown below. Fig.8: this is the 64-pin version of the TQFP Programming Adaptor. It’s a reasonably common package, especially for 32-bit PIC microcontrollers and some PIC16s, PIC18s, PIC24s, dsPIC33s, Atmel ATSAM chips and more. This is basically the same as the other boards but with more socket and header pins. Fig.9: the 64-pin Programming Adaptor set up for the PIC32MX470F512H-120/ PT used in the Micromite Plus. We removed the plastic from some headers for pins 53-55 and 58-60 so they would sit lower and give more clearance for the TQFP socket hinges. They’re still long enough to fit jumpers. sourced a socket, so we decided to make the PCB available to anyone who might need it. TQFP-64 programming rig Again, this circuit is simply that of Fig.2 but with twice as many socket pins and associated header pins. The PCB overlay is shown in Fig.8, with Fig.9 being the minimal configuration for programming a PIC32MX470F512H-120/PT or similar (this should also suit 64-pin dsPICs). Photo 5 shows our jig for programming the PIC32MX470F512H-120/PT. Practical Electronics | October | 2024 We also built a TQFP-64 programming jig for the powerful PIC32MZ2048EFH064-I/PT chip that Phil Prosser likes to use in his projects. As shown in Photo 6, we didn’t use our custom board for this but instead purchased a socket that came on a PCB with 16-pin headers on all four sides (on the underside). We then mounted that on a protoboard via four 16-pin sockets and soldered the bypass capacitors and programming header to that. Connecting the pins to GND, Vdd and the programmer pins was done by point-to- point wiring using Kynar (wire wrap wire), which is thin but stiff and easy to work with. We could have used the custom jig in this role, but we wanted to try a different approach. It was a little work to do this but it worked fine. At the time of writing, this adaptor costs £16, including delivery and can be purchased from pemag.au/link/ abmw TQFP-100 programming rig We haven’t bothered to make a custom 100-pin board for several 33 Constructional Project Photo 6: as an alternative approach, this 64-pin TQFP socket was purchased already fitted to a board with headers on the underside. We then soldered matching sockets on a piece of protoboard and hardwired a programmer for the PIC32MZ. It’s a bit less flexible than the other approach, but it works. Photo 7: this hand-made 100-pin TQFP programming adaptor has served us well, programming all the PIC32MX470 chips for the Explore 100. The added protoboards (joined by two wires across the back, for Vdd & GND) can be unplugged as they are on sockets that fit the pre-existing headers. Parts List – TQFP Programming Adaptors Parts required for all versions 1 6- or 8-pin header, 2.54mm pitch 1 6- or 8-pin right-angle header, 2.54mm pitch 16 M2012/0805 100nF 50V X7R ceramic capacitors 10 small jumper shunts 3 short female-female jumper wires 4 M3 tapped spacers 8 M3 × 6mm panhead machine screws 4 M3 hex nuts 1 serial programmer to suit chip(s) being programmed TQFP-32 programming adaptor 1 double-sided PCB coded 24108231, 95 × 82.5mm 1 TQFP-32 ‘clamshell’ test/programming socket [pemag.au/link/abmy] 24 8-pin headers, 2.54mm pitch TQFP-44 programming adaptor 1 double-sided PCB coded 24108232, 95 × 82.5mm 1 TQFP-44 ‘clamshell’ test/programming socket [pemag.au/link/abmz] 24 11-pin headers, 2.54mm pitch TQFP-48 programming adaptor 1 double-sided PCB coded 24108233, 95 × 82.5mm 1 TQFP-48 clamshell test/programming socket [pemag.au/link/abn0] 24 12-pin headers, 2.54mm pitch TQFP-64 programming adaptor 1 double-sided PCB coded 24108234, 95 × 82.5mm 1 TQFP-64 test/programming socket [pemag.au/link/abn1] 24 16-pin headers, 2.54mm pitch Optional parts for all boards 1 or 2 M3216/1206 SMD LEDs plus 1kW M2012 resistors (for VDD/VCC indication) 1 two-pin female header plus M2012/0805 22μF 6.3V X5R capacitor (for micro pins that need a capacitor to GND) 1+ three-pin female header plus M2012/0805 100nF 50V X7R capacitor (for micro pins that need local bypassing) 1 2×8 pin DIL header, 2.54mm pitch (for extra GND terminals) 2 2×20pin DIL header, 2.54mm pitch (for extra connecting terminals) Extra parts per onboard regulator (up to two regulators per board) 1 LP2951D adjustable linear regulator, SOIC-8 (REG1/REG2) 1 50kW top-adjust multi-turn trimpot (VR1/VR2) 1 27kW 1% M3216/1206 or M2012/0805 SMD resistor 2 4.7μF 25V X5R M2012/0805 SMD ceramic capacitors 1 10nF 50V X7R M2012/0805 SMD ceramic capacitor 1 4-pin header, 2.54mm pitch 1 3-pin header, 2.54mm pitch 1 jumper shunt 34 reasons. The main one is that we have programmed only one 100-pin micro to date, the PIC32MX470F512L-120/ PF used for the Micromite Plus Explore 100. So we only needed a simple fixed jig. We were able to buy a 100-pin socket pre-mounted on a PCB with two pairs of 50-pin DIL headers. It was relatively easy to solder strips of protoboard to these headers and then use that to add bypass capacitors, a programming header and the connections necessary for programming, as shown in Photo 7. It’s a little dusty, but it works! As with the PIC32MZ rig, the protoboard is attached via sockets, so we could theoretically unplug them and change the socket to work for a different micro if we need to. Note the two wires running across the back of the socket that join Vdd and GND between the two sides. The programming header is on the underside of the lefthand board and is just visible in the photo. The point-to-point wiring was done using Kynar wire-wrap wire, as it’s easy to work with. This adaptor costs £26, including delivery at the time of writing, and can be purchased from pemag.au/link/abmx Conclusion These programming rigs are somewhat specialised, but they certainly come in handy when you need them. You might build one when embarking on a project that uses a particular chip, and you could build up a collection over time as you work with micros in different packages. We put some effort into creating these PCBs to make them flexible and easy to work with. So any readers with similar needs would benefit from being able to use our PCBs and follow the same general strategies. PE Practical Electronics | October | 2024