This Instructable is a cautionary tale and the steps taken to salvage inoffensive hardware from clumsy handling.
While hurrying to complete a sensor project, the sudden failure of an Arduino Nano was shrugged off as unfortunate and inconvenient. The failure of a second Nano some days later prompted a review.
Investigation showed that one Nano continued to show Tx activity consistent with the project's sketch when connected via USB but would not open a Windows' port. The second Nano, when powered by 9V through Vin, did open a Windows' port via USB. The most plausible conclusion was the mini USB connector failed on a data line in one case and the VCC or GND in the other.
The first reaction was a grumble about the heavy/inflexible Arduino cable but then the recognition a more likely cause was the manner the pieces had been handled for the sensor project. However tempting, the mini USB cannot be used as a thumb hold in removing an Arduino Nano from some 30 pins of socket.
That the Nanos where not toasted was pleasant news and indeed their final application wouldn’t be affected as the USB was not to be used. These good feeling were augmented by having on-hand a USB-TTL UART Serial Converter Module, unused and slightly forgotten.
The euphoric moment passed quickly with the appreciation of how the standard Arduino world of pin-Dupont wire was going to be enormously time consuming and prone to error. There had to be a better way to rehab the Nanos.
The aspiration for this Instructable is to show the material and methods in constructing an apparatus for readily linking an USB-TTL UART Converter to a moribund Arduino Nano without onerous (for some) point-to-point Dupont wiring.
This Instructable is not meant to infer the USB-TTL UART is the only means of communicating with an Arduino nor that the constructed apparatus is particularly appealing. The potential for using ISP was considered but not thought to improve time expenditure.
This is simply a (paraphrased) "Share what's made".
Step 1: Material
1) Soldering heat sinks
2) Sufficient header socket, curved and straight and male pins
3) Capacitors of nominal value .1µf (optional).
4) Prototype PCB (15x30 here)
5) Wire suitable for solder connections.
4) Third hand.
5) Nail polish with ‘artist’ brush (optional).
6) USB-TTL UART Converter
7) Utility knife (optional)
8) One or more alligator clips (optional).
9) Soldering iron.
Step 2: Design
The design/layout of the apparatus has no requirements beyond achieving the proper connection of the USB-TTL UART pins with the Arduino Nano. As shown in the Fritzing diagram:
- GND connects to Arduino GND
- RX connects to Arduino TX
- TX connects to Arduino RX
- 5V connects to Arduino 5V
- DTR connects to Arduino RST
The USB-TTL UART used in this Instructable utilized the SIL 2104 chip and the converter module included a SMD capacitor on the DTR pin. The need for a capacitor on the DTR pin is explained and documented in several locations including here. The additional .1µf capacitance was added to the circuit to provide the ‘just-in-case’ view.
Step 3: Layout
The only significant feature in the layout is to have 7x15 holes for the Nano, 6 holes for the header and room enough to manoeuvre the connecting wire(s).
Having the Male A USB extend over the edge of the apparatus, while not essential seemed to be an obvious feature.
The 15x30 prototype PCB seems bare minimum but is quite a satisfactory.
Step 4: Construction
As way of explanation of the odd bits of material, some time spent with the nails polish, utility knife, curved and straight header sockets and male header is simply a substitute for making a shopping list and purchasing all the right pieces.
The fabrication of ‘custom’ parts of course is not unique to this Instructable. Even if there is no economy in buying a batch of 40-pin headers, the DIY approach means there is never over or under stock of a particular fitting.
What is offered here is an approach taken to overcome the often-confusing display of shiny tin and black plastic encountered in severing the ‘custom’ from the ‘bulk’ material. The application of some nails polish using fine ‘artist’ brush is helpful in at least these ways:
- marks a cut line, material can be ‘prepped’ with the correct pin count regardless of interruptions
- multiple parts, the number of parts and number of pins can be quite easily verified
- nails polish makes a ‘non-slip’ surface
- appropriate colour provide a contrast that the brain appreciates for focus
To complete the construction for this Instructable, the following pieces were assembled:
- 1-2 pin male header
- 1-6 pin male header
- 1-6 pin curved female socket
- 3-3 pin straight female socket
- 1-4 pin straight female socket
Step 5: Soldering
Fortunately this is not a soldering tutorial and since much depends on the choices made, the details are left to the guide of project images with the following elaboration.
As visible in the above image, the 6 pin male header and 6 pin curved female socket are soldered into a ‘long legged’ socket. The 6 pin male header is soldered to the prototype PCB.
This arrangement is meant to provide a clearance between the USB-TTL Converter and the prototype PCB for electrical separation and room for ‘something’ to restrain the converter. The ‘something’ is the 2 pin male header that will align with the RST and I03 connectors of the converter. Remember the 2-pin header should not short the RST and I03 connectors.
It is recommended the ‘long legged’ socket be soldered and installed such that the converter slopes noticeable from the socket to the front edge of the PCB. In turn the 2 pin male header should be installed such that the pin/holes can be aligned without the converter being forced to its maximum depth in the socket.
The parts can be tweaked until the converter easily ‘snaps’ into place and a USB cable can be connected/disconnected without everything falling apart.
Step 6: Summary
The construction of this apparatus stems from the desire to use two Arduino Nanos where the mini-USB connectors had been damaged by poor handling. The only defence for this handling was the effort needed to prise the Nano from its 30 pins of socket.
The apparatus constructed is intended only for communication with the moribund Nano therefore the number of sockets is reduced; four in one corner and three in each other corner. The force required to insert or extract the Nano is therefore reduced and the resulting space between sockets provides ample area for gripping the Nano PCB rather than the seemingly fragile USB connector.
A second rationale for the apparatus was to avoid the problems that arise (for some) in the Arduino World of pins and Dupont wire. The help for the sad Nano is available without the need to develop arcane chants like “brown to pin 2, green to pin 3” for each rehab.
Finally, there is a personal satisfaction that the USB-TTL Converter remains a ‘free range’ asset, in its original state, available for the next call to duty.