Very small TQFP Atmega 328 breakout board ?

All of the breakout boards that I have seen online for TQFP 328s are intended to breakout all the pins in a breadboard-friendly format.

I am wondering if anyone knows if there is a UK supplier who makes a much smaller board that need not break out all the pins and which would not need standard breadboard spacing - just solder pads for attaching fine wires.

As a minimum I need to have access to Reset, Tx, Rx, Mosi, Miso and SCK, a couple of PWM pins, one analog pin and one other digital pin. Plus Vcc and GND, of course. I intend to use the internal 8MHz oscillator.

I know that, in theory, I could design my own board and get someone to make it but that would require a lot of time-consuming learning and expensive trial and error for something that I may only want one or two pieces.

An even smaller board with the smaller MLF chip would be even better - but the chip would need to be installed as I don't have the gear to that myself.

...R

I’ve been curious about these:

Looks like what you need. 11 digital pins, 4 of which can do analog, PWM on pins 3 and 11, internal osc.

It’s small

Hmmm, they left the reset pin flapping in the breeze.

Minimalist design. It would be easy to add a pull up resistor if necessary.

Thanks for that @ dmjlambert. It is certainly an attractive size. However as far as I can see it does not break out Mosi, Miso and SCK - I want to connect to an nRF24.

...R

It's not a 328, but rather a 32u4. I am intrigued by DF Robot's Beetle, and just ordered a couple to play with.

However as far as I can see it does not break out Mosi, Miso and SCK

Yes, they do -- the connector appears to be 6 pads close together on the bottom side of the PCB. You could solder wires to them, but I think the pads are for a "pogo-pin" connector for programming via ISP.

The photo clearly shows an ATMega328p.

Very poor schematics and documentation!

jremington: Yes, they do

Thanks. I'm going to try to look at the Eagle file - but my internet has been out all day until now.

...R

You can see the ICSP connector on the PDF of the schematic.
Do you just need them for programming?

jremington: ...The photo clearly shows an ATMega328p. ...

If that was for me, yes for sure the Tiny Lily is a 328, I meant the Beetle is a 32u4. Which I like better than the 328 because the extra 500 bytes of RAM has saved my projects more than once!

The Beetle may be good for Robin2's project, too. 20x22mm Beetle is 2.5 times larger in surface area than the 14mm round TinyLili Mini. The ICSP pads look harder to solder on the Beetle. But the Beetle does have 4 PWM pins, that extra RAM and flash, and a resonator or crystal. 1 of the 2 PWM pins on the TinyLili Mini is on the ICSP pads, so that leaves 1 PWM if you're using SPI. ChrisTenone that link you gave to the Beetle has a quote mark in it that prevents the link from working. I have a Beetle and it works just like a Leonardo, and works well if you don't mind the typical Leonardo quirks.

dmjlambert: The Beetle may be good for Robin2's project, too. 20x22mm Beetle is 2.5 times larger in surface area than the 14mm round TinyLili Mini. The ICSP pads look harder to solder on the Beetle. But the Beetle does have 4 PWM pins, that extra RAM and flash, and a resonator or crystal. 1 of the 2 PWM pins on the TinyLili Mini is on the ICSP pads, so that leaves 1 PWM if you're using SPI. ChrisTenone that link you gave to the Beetle has a quote mark in it that prevents the link from working. I have a Beetle and it works just like a Leonardo, and works well if you don't mind the typical Leonardo quirks.

Gaaaarrr. I fixed the link. ( o)(o ) Yeah, I use the Micro often, so I think I'll like the Beetle. And for eight bucks ... :)

Thanks for the link to the Beetle. I think it would be too big. It is wider than the Nano. And I don't need onboard USB.

I haven't had time to study the tiny-lily eagle file yet.

The design I have in mind at the moment requires connecting the device to an nRF24 and to a h-bridge - probably a Pololu DRV8833 - which requires a PWM signal for each direction. I also want to flash an LED and use Avcc to measure the battery voltage.

I got the bright idea earlier today (not yet tested) to put a simple encoder on the motor and drive it to a specified speed rather than a specified PWM. That would require INT0 or INT1.

This is all to drive a battery powered radio controlled 00 Gauge loco. I don't think there is any need to reprogram the chip while it is inside the loco so I can probably just solder temporary wires to it for reprogramming.

At the moment I am cobbling together a bare DIP 328 and an nRF24 to make them fit inside the loco boiler. Hopefully I will have that working tomorrow.

...R

"That would require INT0 or INT1." Or a PCINT

CrossRoads: "That would require INT0 or INT1." Or a PCINT

True. But I want things as easy as possible :)

...R

In case anyone is interested here are a couple of photos of my minimal 328 and nRF24L01+
2016 01 02_DSCF3954_640x480.JPG

2016 01 02_DSCF3956_640x480.JPG

By the way the thick black wire is only temporary.

My aim, perhaps with the tiny lily, is to find a convenient (and cheap) way of making it even smaller.

In the UK HobbyComponents supplies the tiny-lily board. Interestingly there is also a tinylily motor driver that is only 10mm diameter that has a DRV8837 h-bridge.

…R

Small like this?

Thanks, @CrossRoads. Is that board designed to plug onto an nRF24?

I think 25.4 mm square is too big. The tinylily mentioned earlier is only 14mm diameter. The version I have made with the DIP 328 measures about 15mm x 40mm. I think 15mm or 16mm is the practical max along one of the dimensions.

In the project I am working on now there is space for the long 328. A bare DIP 328 is about 34mm long and that won't fit across the width of an OO gauge train.

I guess if there was a DIP Atmel MCU with (say) 16 or 20 pins that includes a USART and SPI it would be sufficient. But my searches have suggested that that capability is only available in 28 pin packages.


There is another limiting factor - cost. I can get a complete 328, wireless + h-bridge on a board no bigger than the nRF24 for about £28.

There needs to be a big saving to justify the hard work of joining lots of small parts together.

That may even mean the the tinylily (£9) plus the tinylily motor driver (£5.50) plus nRF24 (£2) is barely competitive.

...R

15.4mm a good width? With NRF24L01+ socket, and Reset, Tx, Rx, Mosi, Miso and SCK, a couple of PWM pins, one analog pin and one other digital pin. Plus Vcc and GND.
TQFP package vs MLF so it's a little easier to assemble. 0805 R & Cs. 0.1" spaced IO pins. 10uF ceramic cap for the Radio power too.

with gnd planes turned off.