SamR34 Tinker Module


(Mrpackethead) #1

First cut of a module i’m going to build, based on the Microchip SamR34. Capture

Drawn in Altium, if anyone wants the files let me know.


(Jfmateos) #2

Nice work mrpackedhead.
Is it a 2 or 4 layer pcb?


(Mrpackethead) #3

Its 4 layer. it would be pretty much impossible to do as a 2 layer. You need a solid GND plane dedicated to the RF.


(Afremont) #4

Details?


(Mrpackethead) #5

Its using a microchip SAMR34 . I’ve taken some of its IO to the header pins and used a few onboard for the LEDS, and Dip switch, Its got USB that will power it, or you can program it via a battery. There is not a lot more to say really.


(Afremont) #6

I had to get the datasheet out and take a look. Pretty sweet chip. What kind of sleep current are you expecting? The chip itself can go pretty low, but regulators and whatnot can have a big impact, I’m sure you know. Are you putting an external crystal of any kind on it, 32K clock or are you going with the internal clock generators? Next to final question, are you bringing the SWD pins out to a header? Finally, are you planning to run the Microchip LoRa stack or something else? Bonus question for extra credit, are you bringing out the high power output for 17-20dBm. I’m in the US. There are so few really low sleep current boards available it seems. I still haven’t found anything that puts out 30dBm (US max).


(Mrpackethead) #7

I dont’ know what the sleep current will be yet, but I will be able to measure it, and make a pretty educated guess, using the dev board from microchip. It has a LOT of extra stuff on it, that makes it handy to develop with but pretty useless to integrate into a real project and its expensive. As it sits this is just a play thing to get started. My first applicaitons are all for things where they will be class C, and will have lots of power avaialble so getting to picoamps is not a criteria, but it will be in time somethign to do.

It has an osciallator and a and 32k crystal. The SWD pins are standard and are on the 5x2 header, so you can plug in a stock debugger tool.

And yes, It has both the high power and low power stages. I’ll see if i can push the schematic up somewhere.

This is still very much early days


(Nestor Ayuso) #8

can you share the reference of the SPDT or SP3T?


(Mrpackethead) #9

(Nestor Ayuso) #10

I mean the RF switch with QFN12 layout.


#11

In the SAMR34 data-sheet, they use a SKY13373-460LF


(Nestor Ayuso) #12

Thanks,

I am desingning a board and using RFSW8001, the same used in module RAK811.
But SKY13373-460LF truth table feets better for me and Insertion Loss is better
Thanks


(Mrpackethead) #13

Here are the links to the offical microchip development board.

https://www.microchip.com/DevelopmentTools/ProductDetails/dm320111

Untill i can get that working i’m not going ot do much more work on my tinker board, as i need it working for a reference.


(Mrpackethead) #14

Hi, I’ve just finalised my ‘dreamer1’ module design and am sending it to fab today. The motivation behind this was to create a low-cost way ( compared to the Microchip Dev board ) that was easy to prototype conceptual ideas, and or make one-off widgets with. It’s not something I would contemplate making lots of devices with.
dreamer1

The PCB is 43 x 26mm, and the two rows of headers are aligned on a .1" ( 2.54mm ) pitch so it could be plugged into a breadboard.

Its designed to be powered from USB, but you can feed power to it via the header pins, or the BAT pin. It will be possible to program it using the standard ICSP programmer pins, but also via a USB bootloader. There are a reset and user button, two dip switches, and two LEDs onboard. A number of GPIO pins, Serial RX/TX and I2C are taken to the header.

This is largely based on the microchip reference design, however, I have modified it to use 0402 parts as the smallest part size so it is a little more friendly for assembly. The PCB requires some micro vias and a specific stack, which does, unfortunately, drive the cost up a little, but there’s really no way around it.

The design files ( Altium ) are available on GitHub. There is a pdf of the schematic as well. https://github.com/mrpackethead/dreamer1

At present, I’m intending to make 10 of these and see how they go. While I do manufacture electronics, I can’t’ see this being something I’d like to make for sale, as these kinds of things are commoditized already and its a race to the bottom in pricing. If they cost 50c more than the cost of the parts, folks would complain they are too expensive. None the less they are useful to me, and if its useful to someone else then that would be good. I need to do an itemised BOM and work out exactly how much these will cost to make at 10up, and when I do, I’ll add the info to the repo. My educated guestimate is s that including PCB, it would cost around USD$300 to make 10 buying parts from Digikey / Mouser or similar and a PCB from a Chinese PCB shop. doing it at 1000up it should get down to under $10 of parts.