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My Agenda Page
24403visit from 2008-12-12.
Agenda charging...   Issue #1: After I got my Agenda VR3 and build my development environment, after few days I was in trouble:
Each day must charge and change the batteries inside. Therefore I begin to study the Agenda PCB, with the following results...


Issue #2: The Agenda Serial Cable consumes a lot of power. The solution:

Issue #3: Connecting to Win2k/XP over Serial/IRDA port HOWTO... 


The agenda has some circuit on the PCB to deal something with the external power - the documentation assign Pin1 on the bottom connector to it. Looking inside the PCB there is an unsoldered diode connected to this pin. Its positive side connected directly to Pin1, the negative one to the PCB raw power ( there is an up converter also inside the unit producing a stable 3.3V). But the Pin1 also drive a transistor, and if it see some voltage on Pin1, switch off the battery from the raw power. Therefore if you mount the diode and connect 3.3V to Pin1, theoretically the unit will work from the external power. I say theoretically, because the switching transistor base connected directly to Pin1, caused that if the raw power less than the Pin1 voltage, which is always true, there will be an open diode in this transistor...... Maybe you can short-circuit the unmounted diode, but it is obviously dangerous. Somebody can play with this solution also, but my goal was using and charging the unit simultaneously. Therefore one possible solution which satisfy my needs that soldering the missing diode, unsolder the switching transistor and make a short-circuit between the transistor emitter-collector. In this case the battery always connected to the raw power, and over the soldered diode we can charge the battery and drive the unit.
Here is a picture to make the modifications:
The mod..Full size

The two red rectangle show the modifications: the left one is the diode already soldered ( sorry, I have no pics before the mods), the right is the unsoldered transistor place with a small copper line to make a short-circuit. I have a version 9 PCB, as I know, the version 8 Blue Agendas has a white gizmo (spare cap?) glued at the diode's place. Therefore here I publish my full ver. 9 PCB picture:
PCB full 140kByte       PCB full 1.6 MByte

The next issue was to drive the unit over Pin1 with the external voltage. Because the Pin1 connected to other parts of the PCB also and I can't track the whole line ( as I remember, there is an resistor-array connection on the other side of the PCB and there is a resistor at the right side of the red rectangle showing the transistor, etc.) I'm can not choose any classic solution to charge the battery. I got some circuit to make this ( thanks!) but each of this solution can result higher than 3.6V at Pin1. Because I don't know what can this do in the PCB, I choose a quick and dirty solution : from an stabilized 5V power supply I drive the unit over one Schottky and two Si diode ( the light on the picture is for fun: parallel for this two diodes I connected a led to see what happened) In this case there are 3 Si + 1 Schottky diode = 3*0.7V+0.2V=2.3 minus the 5V yield maximum 2.7V at the raw power and max 3.4V at Pin1. Because of the resistive part of the diodes, the charging current also limited somehow. This means that the NiMH accus charged until 1.45V which seems to be high, but in the real life the unit charges an empty accuset within few hours and the charge level is 1.3-1.4V. It is depends on what Agenda doing at that time. This is not a fool-proof solution, because the charging current vary between 100 mA and 0 depending from the accu voltage level and the Agenda power usage. But I think the biggest trouble can be just not to charge the NiMH's 1000 times just say 500, which is acceptable to me ( here in Hungary the NiMH 600mA accus costs 3-5 times more than a good alkaline). Below you can find the schematic of the cradle modification
Cradle mod..

Sorry, but I forgot to make a picture about the cradle modification. This is an easy one: if you open the cradle ( 6 crews) and seeing from the bottom, the right top side of the connector is Pin1 which connected to the circuit described above, Pin2 is the Ground. The above circuit does not need to make a separate PCB panel, you can solder the diodes one-by-one . I don't find any good place to assemble the power connector in the cradle, so two wires going from the cradle to the 5V power male connector.
P.S: After half year of usage I find that the Schottky diode is not necessary when you doesn't leave the Agenda in the cradle for weeks....

The Serial Cable

The Serial Cable contains a special chip, the Sipex 3243 which convert the Agenda 0-3.3V I/O signal to the RS-232 minimum -5-+5V and back. In the original version Agenda use the chip "Auto-Online" function to shut down the transceiver's voltage converter, conserving energy. Unfortunately this function is a simply one: when all the RS232 input is not driven by the connected computer ( the cable unplugged ) disable all input/output driver and his power converter. But when the cable is connected the converter working, eating approx. 10 mA. There are additional possibilities to shut down the converter, for example there is a SHUTDOWN input ( Pin 22 ) which is when low, force the standby mode ( 1uA! ). In the original version this pin connected to the 3.3V VCC, therefore just the Auto-Online works. The ideal solution were if we can drive this pin by the Agenda's inverted DTR signal - but in this case need to mount to the circuit minimum one transistor and a resistor. There is an additional solution: We can watch the other side DTR signal: it is connected to Agenda DSR , over a special input pin of the transceiver - the R2in pin has a normal (inverted) and a special (non-inverted) output, the last one working all the time - therefore if we cut the SHUTDOWN pin from the VCC and connect to the R2out (pin 22) the unit will go to sleep when the computer DTR is inactive ( -12V) and arise when become active (+12V). The corresponding circuit is in the serial cable connector, in the picture below you can find the modifications: the red line shows where you must cut the PCB , the blue one is the Pin 20-Pin22 connection.
The Serial mods...Full size


Connecting to Win2k/XP:

The Agenda Network Menu contains special items for this connection: the "MS Direct Cable Connect" host/guest item. It is not really necessary if you can do the following:
- locate the mdmhayes.inf file in the %Systemroot%/inf directory and edit this text file. In the [M2700Reg] section append the following two lines :
    HKR, Responses, "<h00>~", 1, 08, 00, 00, 00, 00, 00, 00,00,00,00 ; Server side - the client is requesting a connection
    HKR, Responses, "~", 1, 08, 00, 00, 00, 00, 00, 00,00,00,00 ; Server side - the client is requesting a connection
- save the modification, and delete the corresponding .PNF file ( mdmhayes.pnf ).
Now you can set up new "modem" , the Direct Cable connection on serial port and attach it to the RAS server (XP: Incoming connections ). In this way from the Agenda there are no any difference between the Unix/Cisco,etc. and the M$ connection. (The above modification means: when the Direct Cable connection see the PPP start character "~" start the PPP session with the peer, not playing with the CLIENT/CLIENTSERVER strings).
 If you have a real IP subnet on your Ethernet you can also assign two IP address ( from the Ethernet IP subnet!)  for the PPP connection ; this case there are without any additional setting you have a routed, full-featured IP connection to the Agenda.

Connecting over the IRDA port

I was unable to set up it with the core operating system components, so some hacking needed. There is an excellent tool to making virtual COM port from the IRDA on W2k/XP at: http://www.ircomm2k.de/ . After downloading/installing you will have an additional COM port ( in my notebook the COM6 ). With this extra COM port you can make an additional Direct Cable connection - and with this method you can set up a PPP connection over the IRDA port.  The driver set the connection speed to 9600 bps, but the measured (bing) transfer speed vary between 38 and 49 kbps. The service ( Virtual IR COM Port, Service Program ) at least in my machine not very stable - sometimes after dropping the connection it drives the CPU to 100% and after restarting the service manually simply doesn't work. In this case you can deselect/select the virtual com port listening in the Incoming Connections list, after this everything working again. After some playing with it seems to be working perfectly if you never drop the connection, just break the infra link.


If you have any comment/question/suggestion write it to me: János Pálóczi-Horváth