ATtiny Bitsy Spider
Tags: robots, pcb, smd, hm10
Published: 2014-01-04 10:00:00

---
title: ATtiny Bitsy Spider
tags: robots, pcb, smd, hm10
published_at: 20140104T10:00Z
canonical_url: https://ladvien.com/attiny-bitsy-spider
main_image: https://ladvien.com/images/Itsy_Bitsy_Spider.jpg
series: Custom PCBs
published: true
---



[ATtiny Bitsy Spider](/files/ATtiny_85__Serial_talking_to_HM_10_v4.zip)

{% embed https://www.youtube.com/embed/wQFeiCescf0 %}

UPDATE: Added BOM corrections. (Sorry for floating.)

Ok. Here's a finished board I've been working on for a bit.

In essence, it is a BLE node board.  It combines an HM-10 board with an ATtiny 85. This board builds off:

1. [Bluetooth 4.0 (HM-10) ](http://letsmakerobots.com/node/38009)
2. [ATtiny 85](http://letsmakerobots.com/node/39130)

The idea of the Bitsy Spider board is diminutive controller node.  I wanted it to be cheap and versatile enough to use as a node, but I think the final price is around $11 each.

Here's the ole GitHub:

* [ATtiny Bitsy Spider](https://github.com/Ladvien/HM-10) (v.02)

The BOM:

1. [OSHPark Board](http://www.oshpark.com/shared_projectss/dTdbdJec): $1.68 each ($5.05 minimum).
2. 1 x 20k Resistor -- 0402: $.04
3. 3 x 10k Resistor -- 0402: $.04
4. 2 x 1uF 0402 $.20
5. 3 x [BSS138](https://www.google.com/#q=bss138): $.60
6. 1 x [ATtiny 85](http://www.mouser.com/ProductDetail/Atmel/ATtiny85-20SU/?qs=8jWQYweyg6N/GXnwAe4Icw==) -- SOIC: $.80
7. 1 x [HM-10](http://imall.iteadstudio.com/im130614001.html): $6.50
8. 1 x 0603 LED $.11
9. 1 x [3.3V LDO](http://www.mouser.com/Search/ProductDetail.aspx?R=MCP1802T-3302I/OTvirtualkey57940000virtualkey579-MCP1802T-3302IOT) 300mA -- SOT-23-5 - Voltage Regulator: $.58

Total (approximate): **$10.55**

There are lots of solder-jumpers on this board, given it is meant to be versatile.  

Here is the programming pinout to use an Arduino as ISP

![](https://ladvien.com/images/Incy_Blue.jpg)

![](https://ladvien.com/images/Attiny_Bitsy_Spider_--_Solder_Jumpers_for_TX-RX.jpg)The board is intended to harness the serial connection of the HM-10. In this version I made it straight forward, you leave the jumpers between the RX/TX line of the HM-10 and the ATtiny unsoldered, program the ATtiny as many times as you like.  To test your serial connection between the ATtiny and the HM-10 simply breadboard the PCB and put jumpers like so:

**PB0 <---> TX**

** PB1 <---> RX**

This will allow you to test your code, without having to solder and unsolder.  Then, after your code is perfectish, solder the jumpers marked "PB1 & HM10 RX" and "PB0 & HM10 TX," then embed the Bitsy Spider.

![](https://ladvien.com/images/Attiny_Bitsy_Spider_--_Solder_Jumpers_for_Always_On.jpg)This is an option that'll probably continue throughout different versions of the board.  I ran the GND connection of the ATtiny through a N-Chan MOSFET, and tied the gate of the FET to the PIO1. The PIO1 pin of the HM-10's function is for a Connection Status LED.  But one of the options one can set on the HM-10 is for the PIO1 to stay low unless the HM-10 has a connection.  This can be set on the HM-10 when it's in AT mode by typing:

1. Type: **AT+PIO11**
2. Response: OK+PIO11

When done, the ATtiny 85 will only power-up if the HM-10 has a connection.  Of course, the solder-jumper is meant to bypass this feature.

![](https://ladvien.com/images/Attiny_Bitsy_Spider_--_Solder_Jumpers_for_ATtiny_Reset_Control.jpg)The last solder jumper controls the HM-10's reset.  If soldered, the ATtiny 85 can reset the HM-10 by sending PB4 high for ~100mS.  I added this as I hope to create a star-network with the ATtiny Bitsy Spider.  

Here's a summary explanation; the HM-10 has a time out feature after it losses connection from one HM-10 that prevents it from connecting to another for approximately 10 seconds.  So far, there is no option to bypass this "lost connection" time-out.  But resetting the HM-10 (<150mS power-cycle) bypasses this time-out.  I'll update more on this setup when I've completely tested it.  If there are questions, I've written a lot in the comments of my original [HM-10 post](http://letsmakerobots.com/node/38009).  But also feel fre to contact me.

![](https://ladvien.com/images/ATtiny_Bitsy_Spider_--_No_Decoupling.jpg)

One last thing I should mention.  

I expect one major mistake and two minors on the first run of every board I send off.  This board is no exception.  I forgot the decoupling capacitors on the voltage regulator and the HM-10. I've added them on the v.02 board.  Of course, this shouldn't be a major flaw, but with a capacitor on the voltage regulator it causes it to spit out 3.6v instead of 3.3v.  Major problem.  I saved this set of boards by soldering a 0402 1uF between the legs of the SOT-23-5 regulator.  Not fancy, but saved $5.