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PIC and AVR Breakout Boards By Tim Blythman T he three Breakout Boards we designed are intended to plug into a breadboard while also connecting to a Snap or PICkit 4 programmer for power and programming. Two can be used with the four PIC parts we discussed in the feature article: one for SOIC parts and the other for DIP. The circuit for these two boards is identical – see Fig.3. The other is designed for the AVR64DD32 and its circuit is shown in Fig.6. The PICkit 4 cannot provide power in UPDI mode (as for newer AVR chips), so we recommend using a Snap modified to provide 5V with the AVR64DD32. PIC Breakout These PIC Breakout Boards accept SOIC (Fig.4) or DIP (Fig.5) devices up to 20 pins and are designed to provide basic programmer connections and the two passive components needed for a minimal working setup. They break out each pin of the microcontroller to an adjacent header pin. This could be a standard header below to plug into a breadboard, or a header socket above, into which you can plug jumper wires. We’ll describe the parts needed to plug into a breadboard. Many recent 8-bit PIC parts have standard pinouts on their topmost pins, shown as pins 1-4 and 17-20 in Fig.1 (page 45). So this Breakout should work for most recent 8-pin, 14-pin and 20-pin 8-bit PICs, as long as they are placed at the top of the Breakout. You could fit the DIP breakout with a 20-pin narrow IC socket to allow parts to be changed in and out. Alternatively, a narrow ZIF (zero insertion force) socket could be used, turning the Breakout Board into a handy programming jig. Assembly of the PIC Breakout During construction, refer to the appropriate overlay diagram, Fig.4 or Fig.5. Both are double-sided boards, with the SOIC version being 15.5 × 32.5mm and the DIP version being 15 × 35.5mm. If you have the SMD version, start by soldering the microcontroller in place. If it is a 20-pin part, it will be a tight fit, so keep it clear of the pads for the header pins. Apply flux and rest the chip in place, ensuring that pin 1 goes to the end near CON1. 8-pin and 14-pin parts won’t be as fussy as they are narrower but should have their pin 1 in the same location. Tack one lead and check that all the remaining pins are aligned before soldering the others. Check there are no bridges between pins or to the header pin pads; if there are, clean them up with flux, solder braid and a clean iron. Then use an appropriate solvent to remove any remaining flux. If you have the DIP version, solder the socket or IC in place. Like the SMD part, you can tack one lead and then check that the socket or IC is flat and flush before soldering the other leads. Next, solder the capacitor and resistor and trim their leads close to the PCB. To fit and align the header pins, it’s a good idea to plug them into a breadboard first. This will guarantee that the pins will align with the breadboard in the future. Place the PCB over the pins Fig.3: the 20-pin Breakout Board circuit connects the programmer header (CON1) to the chip with all pins also going to a pair of SIL headers. Figs.4 & 5: the breakout boards have been designed for breadboarding or general use (eg, plugging into a pair of SIL sockets). They accept 8, 14 and 20-pin devices with pin 1 in the same position. 50 Silicon Chip Australia's electronics magazine siliconchip.com.au and push it down flat. Tack the corner pins and adjust if necessary before soldering the remaining pins. Finally, fit the right-angled header, CON1. Connect your programmer, being sure to align the arrows that mark pin 1 on both the programmer and the Breakout’s programming header. AVR Breakout The PCB overlay for the 16 × 53.5mm AVR Breakout Board, coded 24110223, is shown in Fig.7. We’ve made it as narrow as possible to conserve breadboard space, resulting in a gap in the middle of the rows of pins. It therefore has 16 pins down each side, but they take up 20 rows on a breadboard. Since there are two main power rails and the VDDIO2 pin for the MVIO feature, there are three bypass capacitors. The jumper shunt connects the two rails, which is necessary for applications that don’t use MVIO. The 1kW resistor on this board is connected between VDD and UPDI. This is discussed in the accompanying article and is necessary if you are using a Snap programmer. Assembling the AVR Breakout The pitch of the TQFP AVR64DD32 chips is finer than SOIC parts, but still Parts List – PIC Breakout Board 1 double-sided PCB coded 24110225, 15.5 × 32.5mm (for SOIC parts) OR 1 double-sided PCB coded 24110222 15 × 35.5mm (for DIP parts) 1 8/14/20 pin PIC16F18xxx microcontroller in SOIC/DIP package 1 20-pin DIL IC socket (optional; for DIP micros) 2 10-way pin headers, 2.54mm pitch 1 5-way right-angle pin header, 2.54mm pitch (CON1) 1 100nF MKT or ceramic capacitor 1 10kW axial 1/4W resistor Parts List – AVR64DD32 Breakout board 1 double-sided PCB coded 24110223, 16 × 53.5mm 4 8-pin headers, 2.54mm pitch 1 4-way right-angle male header, 2.54mm pitch (CON1) 1 2-way header and jumper shunt, 2.54mm pitch (JP1) 3 100nF MKT or ceramic capacitors 1 1kW axial 1/4W resistor 1 AVR64DD32-I/PT 8-bit microcontroller, TQFP-32 (7×7mm) (IC1) not too difficult to solder. Apply flux and rest the part roughly in place, ensuring pin 1 is in the correct location, then tack one lead. Take care to check that all four sides are aligned before tacking another pin on an opposite corner, then soldering all the remaining leads. Remember that you can use flux, solder wicking braid and a clean iron to remove any bridges. Fit the three capacitors next and follow with the 1kW resistor if that is needed. JP1 can be installed next. You should leave the jumper shunt in place unless you plan to connect an alternative VDDIO2 supply and activate MVIO. Like the DIP PIC Breakout, you can align the header pins by pushing them into a breadboard first. Leave a gap of four rows in the middle, then push the PCB down firmly before soldering the pins. Finally, fit the four-way header (CON1) for the programmer and attach the programmer. The arrow marks pin 1 and the programmer should have a corresponding mark. MPLAB X If you haven’t used the MPLAB X IDE before, see our feature in the January 2021 issue (siliconchip.au/ Article/14707). If you need to manually install the DFP (device family pack) for the AVR64DD32 or any of the PIC parts, use the Tools → Packs SC menu item. Fig.6: The AVR64DD32 Breakout Board is similar but brings the pins out to four headers as the chip has pins on four sides. Fig.7: the four headers are arranged in two rows so they can be plugged into a breadboard. The gaps mean the board is narrow enough for a standard breadboard. siliconchip.com.au Australia's electronics magazine October 2022  51