Thank you for your answer. I check with an oscilloscope and find out the bug. It was in the code I wrote for managing the Digital I/O. Very simple error but sometimes those are the most difficult to debug. In fact once I I2C.Write a value on the Digital port the changed bit is of course kept in the values that are I2C.Read later. I changed the code making independent the I2C.Read from the first two bits that are used for the Relays control, and that solved the problem.
Franco Di Persio. -----Mensaje original----- De: Michael Schippling [mailto:sc...@santafe.edu] Enviado el: martes, 17 de julio de 2012 20:00 Para: francodipersio CC: tinyos-help@millennium.berkeley.edu Asunto: Re: [Tinyos-help] I2C problem in micaz and MDA300 Try to compare the low level I2C code and see what's different between T1 and T2. I think the last version of T1 had the atmega code in: tinyos-1.x/tos/platform/avrmote/HPLI2CM.nc If you search for "schip tinyos I2C" you'll find some help list discussion of my battles with the Moteworks all-in-software bit banging code used by the iris in: MoteWorks/tos/platform/atm128/I2CM.nc Specifically the spec calls for a "wait state" mechanism driven by the slave device which was not implemented in the software. I would hope that a hardware impl does this correctly, but who knows... I found this datasheet to have a good description of I2C operation if you need to start poking an oscilloscope or logic analyzer at it: http://www.nxp.com/acrobat_download/usermanuals/UM10204_3.pdf MS francodipersio wrote: > Hi, > > > > I am using Micaz and Tinyos-2.1.1 together with the MDA300 sensorboard. > > Taking as base the code from > http://tinyos.cvs.sourceforge.net/viewvc/tinyos/tinyos-2.x-contrib/uoit/mda3 00ca/ > , I am actually trying to complete the driver for controlling the > 8-Channel Digital I/O. > > On MDA300 the hardware component proposed for the 8-Channel Digital I/O > is the PCF8574A and its work via the I2C interface. Two of the 8 > channels are used for controlling two Relays. > > In order to control the I2C bus I am using the codes from > .tos\chips\atm128\i2c (by the way, I have downloaded the last version > from the trunk). > > At power on, the 8 channel ports on the PCF8574A are high (value 0xFF) > > I have no problem in reading the data from the device, once an Interrupt > change from high to low the correspondent pin on the 8 channel ports, > but the problems arise when I try to write on the device in order to > control the two relays. In this case the PCF8574A stop to work. I am > sure is not a hardware problem, because with the Tinyos-1.x everything > is working properly. > > In order to debug the problem I check the Atm128I2CMasterPacketP.nc > file, but apparently everything goes smoothly being the status codes > called by I2C.status the proper ones (table 88 - Status Codes for > Master Transmitter Mode in the ATmega128 Manual) along the writing process. > > So, I presume that something wrong is happening after data has been > transmitted and ACK has been received, thus during and after the STOP > condition is sent. > > Also I have noted that the data is reaching the device, because I > verified that the correspondent bit on the PCF8574A port is effectively > changed, but after that the device become irresponsive. Also, if I try > to write the default value (0xFF) and in this case everything go fine > and the device keep working. > > > > Somebody has any idea how to solve the problem? > > There is a way with the Atm128I2CMasterPacketP to check the status just > before and after the STOP condition is sent? > > I should check with an oscilloscope the I2C behaviour, but I am not so > familiar with them, so I hope to solve the problem in other way. > > > > Thank you in advance > > > > Franco Di Persio > > > > > ------------------------------------------------------------------------ > > _______________________________________________ > Tinyos-help mailing list > Tinyos-help@millennium.berkeley.edu > https://www.millennium.berkeley.edu/cgi-bin/mailman/listinfo/tinyos-help _______________________________________________ Tinyos-help mailing list Tinyos-help@millennium.berkeley.edu https://www.millennium.berkeley.edu/cgi-bin/mailman/listinfo/tinyos-help
