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Forum Index : Microcontroller and PC projects : I2c to RS232
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| Gadget Regular Member  Joined: 22/06/2011 Location: AustraliaPosts: 70 |
Now we have I2C communications, anyone know of a convertor/chip/circuit that can be used to get RS232 comms? I ask as I have a plasmatronics PL20 solar regulator and the RS232 interface, and have managed to get all the tech details (source code etc) for their PLCOMM program. So I am thinking I could program the maximite to 'talk' to the PL20 and act as a real time datalogger instead of using a PC. any input would be greatly appreciated. Regards Terry |
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Gizmo Admin Group  Joined: 05/06/2004 Location: AustraliaPosts: 5078 |
Hi Terry You could use a PicAxe chip to convert I2C to RS232 and back. Have you used the PicAxe chips before? I think Geoff will be adding RS232 to the Maximite in time. Glenn The best time to plant a tree was twenty years ago, the second best time is right now. JAQ |
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| Gadget Regular Member Joined: 22/06/2011 Location: AustraliaPosts: 70 |
I should have thought of that, I have a few PicAxes at home Thanks for the hint Glenn |
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donmck Guru  Joined: 09/06/2011 Location: AustraliaPosts: 1313 |
I know Stuart was chasing some I2C to UARTs, several have spoken about using a cheap pic chip programmed to suit, and the PicAxe is possibly a solution that will do the job. Yes Geoff will have it working eventually, but like I2C, I'll bet users will find a solution first. After all, why not have several UARTs. There will be an eventual call for them. Cheers Don... https://www.dontronics.com |
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ksdesigns Senior Member  Joined: 25/06/2011 Location: United StatesPosts: 143 |
I have a pic version using a pic12f1822 about done just need to test some more. its a cheap 8 pin part and you can change the i2c address on it and have multiple of them on the i2c bus. will be able to do handshake hardware and software and also rs485 with 9 bit addressing . hope to have the source up this week .. then after that will have a onewire version ken |
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| donmck Guru Joined: 09/06/2011 Location: AustraliaPosts: 1313 |
Nice Ken, A buck a chip pretty much in reasonable quantities, or $1.20USD in one off. [code] Enhanced Mid-range Core with 49 Instruction, 16 Stack Levels Flash Program Memory with self read/write capability Internal 32MHz oscillator Integrated Capacitive mTouch Sensing Module Data Signal Modulator Module MI2C, SPI, EUSART w/auto baud ECCP (Enhanced/Capture Compare PWM) Module Comparator with selectable Voltage Reference 4 Channel 10b ADC with Voltage Reference 25mA Source/Sink current I/O Two 8-bit Timers (TMR0/TMR2) One 16-bit Timer (TMR1) Extended Watchdog Timer (EWDT) Enhanced Power-On/Off-Reset Brown-Out Reset (BOR) In Circuit Serial Programming (ICSP) On Board In-Circuit Debug Wide Operating Voltage (1.8V – 5.5V) Low Power PIC12LF182x variants (1.8V – 3.6V) Standby Current (PIC12LF182X): 20 nA @ 1.8V, typical Active Current(PIC12LF1822): 50 uA/MHz @ 1.8V, typical [/code] [code] Parameter Name Value Program Memory Type Flash Program Memory (KB) 3.5 CPU Speed (MIPS) 8 RAM Bytes 128 Data EEPROM (bytes) 256 Digital Communication Peripherals 1-A/E/USART, 1-MSSP(SPI/I2C) Capture/Compare/PWM Peripherals 1 ECCP Timers 2 x 8-bit, 1 x 16-bit ADC 4 ch, 10-bit Comparators 1 Temperature Range (C) -40 to 125 Operating Voltage Range (V) 1.8 to 5.5 Pin Count 8 XLP Yes Cap Touch Channels 4 [/code] Will it do the dishes? 
Cheers Don... https://www.dontronics.com |
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jman Guru Joined: 12/06/2011 Location: New ZealandPosts: 711 |
then after that will have a onewire version Yippie DS1820B here we come John |
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stuarts Senior Member Joined: 15/06/2011 Location: AustraliaPosts: 199 |
I have some 16is740's (single uart) that I am intending to get up and running. there are also the 16is750/752/760 that are dual uarts. they have dual address lines so you could have 4 of them running, therefore 8 rs232 ports. Just been a bit tied up at work and had to put it on the backburner. then the burner went out. Stuart Time is nature's way of keeping everything from happening all at once. |
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Geoffg Guru Joined: 06/06/2011 Location: AustraliaPosts: 3194 |
There must be a chip in the Microchip or other library that has I2C, serial, PWM and SPI. With just a little programming it could act as an I2C slave and receive commands to control the serial, PWM and SPI peripherals. It would be the magic Maximite peripheral... want 3 PWM? Just add 3 of these chips. All it needs is the firmware? Does anyone have the spare time? Geoff Geoff Graham - http://geoffg.net |
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vasi Guru Joined: 23/03/2007 Location: RomaniaPosts: 1697 |
This is a great idea. The chip must be a 5V one for easy interfacing. But I propose to be interfaced with Maximite via serial UART at 115200 bps. Then, a command protocol can be implemented, as in UBW or Firmata (or just use an adapted version of UBW firmware for serial instead of USB). It can be PIC18F25K22/PIC18F45K22 (PIC18F26K22PIC18F46K22 are not yet easily obtained) for a speed of 16MIPS. But maybe there are cheaper alternatives... This way, Maximite I/O can be reserved for the computer own use (extra RAM memory, etc.) Vasi --------------- But Maximite already use SPI bus and if we connect the additional micro there, it will require only one pin instead of two, without changing the hardware dramatically. In fact, will require only additional connectors and without implementing the serial comm. Hobbit name: Togo Toadfoot of Frogmorton Elvish name: Mablung Miriel Beyound Arduino Lang |
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| donmck Guru Joined: 09/06/2011 Location: AustraliaPosts: 1313 |
Are we after a $1 solution that will give us what we want, and not change the hardware at all? I'm not sure I am following you 100% Vasi. If MM-Basic is already using SPI, then we would have to do hardware changes to be able to use it? [code] Options SPI is already being used, and would require hardware and software changes. Serial Uart is already being used and would require hardware and software changes. I2C is a 2 wire system that MM-Basic already controls, and it appears on the 20 pin bus. Is I2C lacking in speed when compared to SPI or serial? [/code] What Geoff said seems to make sense to me. Many people are working on simple solutions to convert from I2C to whatever it is they need. If a $1 micro is all that is standing in the way, why not look seriously at this solution if speed isn't a problem. After all, we could throw an $8 PIC32 micro at the problem, and have it all duplicated again.
I can imagine the I2C pins running around an external board to various slave devices, with level conversion if needed, such as 232, 485, and suitable connectors attached. This could be a shield type device, or a parallel bus board. Would be nice if the board was also a PIC programmer for the 8 pin devices.
Cheers Don... https://www.dontronics.com |
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| Gizmo Admin Group Joined: 05/06/2004 Location: AustraliaPosts: 5078 |
I see a market for this sort of thing ( hint hint Don  ).
I had a play around with using I2C from the Maximite to talk to a PicAxe in this thread http://www.thebackshed.com/forum/forum_posts.asp?TID=3843&PN =2, with the intention of adding features, especially PWM and Serial, to the Maximite. It worked fine, but you still need to program the PicAxe chip, and you need to download the PicAxe editor to do that. Plus a PicAxe is worth more than its bare bones chip. If someone could supply PIC chips pre-programmed to act as a I2C slave with various outputs, I think they would sell. A single 8pin chip ( not that surface mount stuff, too hard to use for average Jo ) could have a couple of functions, like a pin for PWM, one for Serial, one for Servo, etc. Glenn The best time to plant a tree was twenty years ago, the second best time is right now. JAQ |
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| donmck Guru Joined: 09/06/2011 Location: AustraliaPosts: 1313 |
Simple 8 pin DIP chips, was the way I saw it too Glenn. I also saw an I2C clock and battery backup on the board, as this is a trivial device. I also see other stuff, but it hinges on coming up with a common chip (if possible) that will do everything required, and the hex code to do the magic. And maybe an on board programmer so that users can knit their own. I assume the hex code will need ID addressing of some sort. Cheers Don... https://www.dontronics.com |
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| vasi Guru Joined: 23/03/2007 Location: RomaniaPosts: 1697 |
Well, I understand UART is out of question... I thought at an 18F 28-40pin microcontroller included inside, connected on an already occupied/used bus (SPI), letting Maximite connector(only one pin from there used as Chip Select for microcontroller - don't know if Maximite have free unused pins not available on connector) and I2C free for other uses, and providing additional functionality and free pins (parallel port output, PWM, ADC, etc.) on another extension connector. Anyway, bad idea... unwanted complications... Vasi Hobbit name: Togo Toadfoot of Frogmorton Elvish name: Mablung Miriel Beyound Arduino Lang |
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jebz Regular Member Joined: 13/06/2011 Location: AustraliaPosts: 79 |
Have you coded any pic12f1822 with i2c to serial or other functions you can share? |
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