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Even More PICAXE Developments . . . As well as the new PICAXE 14-M introduced over the past few pages, Revolution Education Ltd, the UK based developers of the PICAXE system, have been hard at work for the last few months. Clive Seager talks us through the latest PICAXE developments. PICAXE 14-M +V Serial in ADC 4 /input 4 Infrain/Input 3 Input 2 Input 1 ADC 0 / Input 0 PICAXE-28X1 1 14 2 13 3 12 4 11 5 10 6 9 7 8 0V Output 0 / Serial Out / Infraout Output 1 Output 2 Output 3 Output 4 Output 5 The new PICAXE-14M has been primarily designed for those 08M projects “when you need just one more input / output!”. The main difference is that the 14M has 11 i/o pins (5 inputs and 6 outputs), as opposed to the 08M’s 5 i/o pins. The pin-out of the new chip is shown in figure X, and those of you who like to use stripboard or breadboards to test out your projects will be pleased to see the very straight forward ‘inputs on left – outputs on right’ layout. V+ 08M 0V RXD OUT0 IN4 OUT1 IN3 OUT2 IN2 OUT3 IN1 OUT4 IN0 OUT5 14M Apart from the pin-count, the 14M is almost identical to the 08M, with the same memory capacity (approximately 80 lines of code) and music ring tone commands. The 08M and 14M are also pin compatible, so with care it is also possible to design a system that will support both parts. Reset ADC0 / In a0 / ULPWU ADC1 / In a1 ADC2 / In a2 ADC 3 /in a3 Serial In Serial Out 0V Resonator Resonator In0 / Out c0 / timer clk In1 / Out c1 / pwm1 In2 / Out c2 / pwm2 In3 / Out c3 / i2c scl / spi sck 1 28 2 27 3 26 4 25 5 24 6 23 7 22 8 21 9 20 10 19 11 18 12 17 13 16 14 15 Output 7 Output 6 Output 5 Output 4 Output 3 Output 2 Output 1 Output 0 +V 0V In 7 / Out c7 / ser rx kb data In 6 / Out c6 / ser tx / kb clk In 5 / Out c5 / spi sdo In 4 / Out c4 / i2c sda / spi sdi and features at an equivalent, or even lower, cost. Therefore Revolution have recently announced the launch of the PICAXE-28X1, which is based upon the new PIC16F866, and supersedes both the 28A and 28X. The 28X1 is pin and program compatible with previous versions, so to upgrade an existing design you can simply swap chips over. However the new 28X1 has a much larger memory capacity, which in turn means more features and support for a longer user program. In fact the 28X1 is a complete new ‘generation’ of PICAXE chip, in which the compilers and bootstrap firmware have been completely re-written. At the same time Revolution have tried to include all the commonly requested extra features from customers. 28X1 New Features Program / Data Memory PICAXE-28X1 The original PICAXE chip, the PICAXE-28A, was based upon one of the very first ‘self re-writeable’ PIC chips that Microchip produced, the PIC16F872. This was later followed by the enhanced PICAXE-28X, based upon the PIC16F873A. However, as microcontroller technologies have progressed, both these PICs have now been effectively superseded by a new generation of PIC chips, which have additional memory 78  Silicon Chip The 28X1 program memory capacity has been doubled to 4096 bytes. This equates to approximately 1000 lines of BASIC code. The data eeprom memory (for read/write commands) has also been doubled to 256 bytes. Variables The 28X1 directly accessible variables (b0, b1 etc.) have also been doubled to 28 bytes (14 words). However a completely new feature is the scratchpad, which is a new separate, additional 128 byte RAM area for rapid saving of siliconchip.com.au CON2 +4.5V* temporary variable data. A common example of use would DB9 IO PROGRAMMING RESISTORS CHANNELS 2 be in saving a long received serial data stream from a GPS module or for storing arrays. λ via the 330Ω∗ 3 scratchpad address can be directly Each accessed 1 2 13 OUT0 PUT and GET commands. However a more versatile use is 22k RXD EQUIVALENT λ 330Ω∗ PICAXE 10k(scratch pad pointer), via the5 ptr 3 08M 12 which is a unique virtual OUT1 FOOTPRINT ‘pointer variable’. IN4 λ 330Ω∗ 11 The pseudo variable4 name ‘<at>ptr’ can then be used in 6x IN3 OUT2 PROGRAM commands as if it was a PICAXE normal variable330Ω∗ but in λuse actuLEDS EDITOR 10 ally to the5 current address on the scratchpad (TO‘reads/writes’ PC 14M IN2 OUT3 SERIAL PORT) pointed to by ptr. Similarly if ‘<at>ptrinc’ is330Ω∗ used as aλ variable 9 6 in a command, read/write is to theOUT4 current pointer address IN1 λ to point 330Ω∗ K and then Kthe pointer (ptr) automatically increments 8 7 14 LEDS A A IN0 OUT5 to the next address. PICAXE Therefore ‘<at>ptrinc’ can be* WITH repetitively RED, GREEN ORused YELLOW in LEDS com14M SUPPLY CAN BE 3V AND 330 Ω 7 mands such as serin to save data in different scratchpad RESISTORS CAN BE OMITTED 14 addresses1 e.g. Hibernate / Sleep 2007 new Picaxe 14m – led chaser Reset ptr = 10 serin 1,N2400, <at>ptrinc, <at>ptrinc, <at>ptr The reset command will reset the chip, clearing variable values and restarting the program. In this example the three serial bytes received will be saved in scratchpad positions 10, 11 and 12 and can then be later accessed, for example, by GET commands. An additional 96 bytes of memory are available via the traditional peek/poke commands and so the 28X1 now has over 250 user byte variables. Setint Resonator a) Serial Communications SC The 28X1 can use either an internal (max. 8MHz) or external (max. 20MHz) resonator. The setfreq command is used to switch between frequencies (internal and external frequencies may be used within the same program). To reduce PCB costs/simplify circuits the resonator may be totally omitted if desired. If the external resonator fails, operation will automatically drop back to the 4MHz internal resonator. Some commands with specific timing (eg, readtemp or irout) always use the internal resonator, switching back to normal timing after the command completes. New Commands Table/Readtable A 256 byte data lookup table can now be defined when the program is written and automatically downloaded (as part of the program) into the 28X1. This is a very convenient and efficient way of storing data, eg, for storing LCD menu text, calibration values etc. The new hibernate command enters a permanent low power sleep state. The 28X1 can then only be woken by a hardware interrupt, eg, a hardware serial or i2c reception. Play / Tune The 28X1 supports the mobile phone ring tone play and tune commands (as 08M) on any output pin. Calibadc The ADC reading within PICAXE chips is based upon the supply voltage, which can sometimes vary over time (eg, as a battery runs down). The new calibadc command uses a fixed internal 0.6V source to provide a known voltage ADC reading. This enables users to calibrate their ADC readings to a known fixed voltage, regardless of battery state. The polled interrupt now also has the option to operate when a condition is NOT true, as well as the original ’match condition’ option. Enhanced Peripheral interfacing Serial communication can now be carried out in three different ways: 1) serin/serout act via the standard input/output pins as before. However the serin commands now support a timeout feature. 2) serrxd and sertxd act via the PICAXE download cable. This enables user program data to be both transmitted and received via the download pins of the 28X1. 3) hserin and hserout are a more advanced method of communication via the on-board serial hardware pins. This allows advanced features such as wake-up from sleep, background receive and much higher serial baud rates. The background receive allows serial data to be automatically saved into the scratchpad area as the PICAXE chip completes other tasks. b) I2C The 28X1 can now act as an I2C master or I2C slave. The new slave mode is fully automatic and is the rec- Pauseus 5V The additional pauseus command creates a smaller time delay than pause. Pauseus operates in 10us multiples. MASTER Timer Data – SDA The 28X1contains a general use 16 bit background timer/ counter. When in timer mode this timer runs in the background at a user defined frequency (eg every second). The timer variable can be read at any time. Timer overflow is used to set a flag bit (toflag). When in counter mode, the timer records the number of rising edge pulses on input 0. This occurs in the background, while the PICAXE program performs other tasks. siliconchip.com.au 5V 4.7k 4.7k Clock – SCL 0V 5V SLAVE 1 SCL 5V UP T0 120 SLAVES ARE SUPPORTED SLAVE 2 SCL SDA SDA 0V 0V 0V June 2007  79 ommended method of networking multiple PICAXE-28X1 chips. The slave features are completely automatic, so the PICAXE chip acting as a slave can still run a normal program, with the I2C slave read and writes occurring in the background without program intervention. The I2C interface operates in the same manner as the popular 24LCxx EEPROM chips, with the 128 scratchpad bytes as the read/write memory area. This method theoretically allows one 28X1 master to control over 120 28X1 slaves, all connected via a common two wire I2C bus. However the software has also been enhanced and now supports improved compilers for all PICAXE chips. The enhanced compilers support many new programming structures, such as ‘do…loop’, ’if…elseif…endif’ and ‘select case’ to simplify the process of writing PICAXE programs. To use these new structures simply make sure you have selected the ‘enhanced compiler’ from the View>Options>Editor menu. Simulation c) SPI (3 wire) The 28X1 supports 3-wire (SPI) communications on input/output pins or via the dedicated hardware pins (which provide a faster transfer rate). Normal input/output pin support is included to allow both i2c and SPI on the same system (as hardware SPI and hardware i2c use the same pins). d) Infrared The 28X1 supports infrared input (with timeout) and output. Sony SIRC format. e) One Wire The 28X1 fully supports the Dallas/Maxim 1-wire protocol, allowing direct control of all 1-wire parts. Enhanced Mathematical Capability The 28X1 has enhanced mathematical capabilities, such as support for brackets within mathematical statements: eg, let b4 = b1 + (b2*5) A number of new mathematical and trigonometric functions (sin, cos, sqr, <<, >> etc) are now supported, as well as new commands for converting number types (eg bintobcd, bintoascii etc.) Another new feature within the software is the ability to simulate, and single-step through BASIC program listings. This allows you to try out your BASIC programs before they are even downloaded to the PICAXE chip. During simulation, each line is highlighted as it is carried out and an on-screen graphic of the PICAXE chip enables inputs to be changed and the state of output pins to be studied. Naturally all variables can also be viewed as the program simulates. Summary Programming Editor Software The free PICAXE Programming Editor software has been updated to support the new 14M and 28X1 new parts. Please make sure you are now using version 5.1.0 or later – if you need to upgrade, a free patch is available on the www.picaxe.co.uk website. The new PICAXE-14M, PICAXE-28X1 (and the new 40 pin option, PICAXE-40X1) provide a range of enhanced features and/or pinout options compared with existing PICAXE parts. For further details please visit the PICAXE website at www.picaxe.co.uk SC Next month: We look at putting thePage 28X1 30/3/07 2:12 PM 1 to work, creating a PICAXE MP3 player. RF_SiliconChip_60x181mm.qxd Enhanced Compiler ELECTRO CHEMICALS Chemical Technology 80  Silicon Chip • Dust Off • Freezing Spray • Electronic Cleaning Solvent No. 1 • Electronic Circuit Board Cleaner • Electrical Contact Cleaner Lubricant • Video Head Cleaner • Ultrasonic Bath Cleaner • Isopropyl Alcohol • Protek • Contact Treatment Grease • Contact Treatment Oil • Solvent Diluted Oil • Contact Cleaning Strip • Circuit Board Lacquer • Q43 – Silicon Grease Compound • Heat Sink Compound Contact us to find your nearest distributor: sales<at>rfoot.com.au Tel: 02 9979 8311 Fax: 02 9979 8098 Richard Foot Pty Ltd, 14/2 Apollo Street,Warriewood NSW 2102 siliconchip.com.au