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This project is an offshoot of an earlier investigation of wireless wearables using the MSP430G2553: http://forum.43oh.com/topic/10060-msp430-wearable-with-radio/. The concept has been successfully tested and is described below. I plan regular updates as the project progresses. The objective is to develop a wearable powered by a coin cell that can be controlled remotely. It could be used, as an example, in the tiara below or on a costume worn by dancers in a performance and controlled from offstage. In the photo an earlier MSP430G2553 coin cell powered wearable is attached to the tiara and driving 3 WS2812 LEDs. The constraints are: cost - unit cost for the receiver of $10 or less technology - common off the shelf components, MSP430G2553 construction - standard double sided PCB spec, keep SMD parts large enough to be hand soldered power - CR2032 (rated 3V and 225 mAH) life - needs to run at least half an hour on fresh batteries reception - 10m with clear line of sight, update at least every 100 ms transmission - desirable but not required size - 40mm/1.6" diameter for receiver programming - Energia desirable schedule - 6 month completion The transmitter will probably be placed on a "Booster Pack" for a LaunchPad running Energia. Multiple LEDs will be driven to gain extra distance, and if required multiple transmitters could be set up from different angles to assure good reception. A display would be helpful as on the FR6989 shown below with an IR LED. The initial Energia transmission sketch to test the concept is located here: https://github.com/fmilburn3/Infrared/blob/master/IR_sendByte.ino. The sketch was developed in Energia V17 using a MSP430G2553 LaunchPad and a 940 nm infrared LED. It loops from 0 to 255 and sends a single byte with the count via infrared to the receiver when a button is pushed. The packets for sending bytes do not follow an existing protocol. It is specific to this application and developed with the goal of getting a byte transmitted at least every 100 ms. The receiver will be a custom MSP430G2553 board powered by a coin cell with a TSOP38238 IR receiver. There will LEDs on the PCB and it will also have the capability to drive LEDs off board. The preliminary receiver code was written in C using CCS and direct register access: https://github.com/fmilburn3/Infrared/blob/master/IR_Receiver/main.c . The framework for the code is based on a post by RobG here on 43oh. The receiver takes transmissions from the Energia sketch linked above and outputs the current byte on eight LEDs in binary form. When the last byte is received it clears the LEDs and outputs the number of bytes received in error out of the expected 255. This allows analysis of reception at different distances and conditions. Shown below is the preliminary testing setup. In the foreground is the G2553 receiver with a TSOP38238 and output LEDs on a breadboard. Middle ground is a G2553 with the infrared LED sending bytes. Background is output from the receiver being monitored on an oscilloscope. The output of the TSOP38238 is quite clean and no errors were seen with the transmitter and receiver this close together. Transmission is at approximately 1000 bytes per minute or 16+ bytes/sec which is within the desired range. I subsequently modified the test setup to run off batteries so I could do some preliminary distance testing. With clear line of sight reception I saw no errors up to 5 meters with one transmission LED aimed directly at the receiver. Errors crept in after that, especially if the transmission is off to one side, not pointed directly at the receiver, or at a greater distance. Near term activities: increase the number of transmission LEDs evaluate the impact of off-center transmission further test in an environment that doesn't have reflective surfaces add WS2812 driver capability and investigating the impact of TSOP38238 interrupts on the WS2812 driver evaluate 2032 battery life further
After making the wearable MSP430 for Halloween this year I was requested to make more for a children's dance group. I have a question, but first some background. This is the latest version: Everything works fine. I use an adapter with pogo pins to program it as shown in the photo. There are three LEDs on the PCB, a push button switch for the user, and more accessible pins than the previous version. Parts are TSSOP and 0805 SMD. Snap fasteners and stainless thread can be used to connect it to LEDs on the costume. A CR2032 coin cell is used to power it (coin cell holder is on the backside of the PCB). So far that has been sufficient and the light weight and inconspicuous nature has been advantageous for the small children it is intended for. Now a new upgrade has been requested... add a radio so that multiple units can be synched and/or controlled offstage. Here is a rough list of requirements: must be inexpensive - current materials for 10 units is less than $5. I want to keep it under $10. keep SMD parts large enough to be hand soldered keep using CR2032 (rated 3V and 225 mAH) The MSP430G2553 and LEDs are currently using no more than 20 mA on average - to be safe assume 40 mA Unit needs to run at least half an hour on fresh batteries Unit needs reliable radio reception at 10m with clear line of sight Unit will need to receive only - no transmission. Reception updates required close to continuously - say every 100 ms keep PCB to the same size - 40mm/1.6" diameter needs to be programmable in Energia I have a fair amount of time - 6 months to get it working I have looked at several different radios but the two that I have experience with are the nRF24L01 and CC2650. I am ruling out the CC2650 due to cost. There is a small version of the nRF24L01 that is shown below for scale along with the more commonly seen version: I think I can shift things around and make this fit. Connection is by the castellated edge facing forward on the photograph. The datasheet states 13.5 mA RX at 2Mbps air data rate. That is in the range of what I have seen as well so it looks like it would meet the requirements. Here are my questions: 1) Is there another radio I should be looking at? Maybe one made by Hope. 2) I have no design experience with radios but could I use an off the shelf design and put the radio, bits, and PCB trace antenna on the PCB myself? I would probably have to give on the 0805 parts size criteria. 3) Any other thoughts, comments, and suggestions appreciated. This will be an open source design and anyone who wants to contribute or have the design is welcome EDIT: the material cost is on a per unit basis
If you have one of those 5050/WS2811 aka WS2812 strips and you want to "wear" it, I have a board for you. Here are the specs: 20pin MSP430G2xx3 5V power supply 0.05" programming header UART input (allows pixel or sequence control) 11mm wide (0.45") 25mm long (1") 32mm long (1.25") - version with memory optional SOIC SRAM or EEPROM 1mm thick There are 4 boards on the panel, 2 with memory option. Assembled boards Board in the sleeve Board attached to 30 LED strip (0.5m)