I'm working on using my Axim x50v palm to communicate with the MJLJ. The RX pin on the Axim is listed as 3.3v-5v. What is the max voltage the MJLJ can send via the serial port. Any ideas?
Jax2A
Max Voltage?
Moderators: JeffC, rdoherty, stieg, brentp
MAX232 Voltage
Jax2A,
The MJLJ send serial data via the MAX232 chip. According to the data sheet on this chip it is designed to produce a data stream using a typical value of +/-8v. Basically the chip takes to 5v supply and uses the capacitors to double it to 10v then inverts it to get +10v & -10V this is used to create the signal on the serial port. so without a load attached (resistance) the volage would swing from +10v to -10v, however the typical value is +8v & -8v when load is attached (ie a computer). It does state that the worst case would be +/-5v, but this is only achieved if the +/10v is also being used to power other devises at the same time (not the case in MJLJ). So I would suggest that you will need something to lower the 8v signal to below 5v.
Regards
Simon
PS. The datasheet can be found @ http://pdfserv.maxim-ic.com/en/ds/MAX220-MAX249.pdf
The MJLJ send serial data via the MAX232 chip. According to the data sheet on this chip it is designed to produce a data stream using a typical value of +/-8v. Basically the chip takes to 5v supply and uses the capacitors to double it to 10v then inverts it to get +10v & -10V this is used to create the signal on the serial port. so without a load attached (resistance) the volage would swing from +10v to -10v, however the typical value is +8v & -8v when load is attached (ie a computer). It does state that the worst case would be +/-5v, but this is only achieved if the +/10v is also being used to power other devises at the same time (not the case in MJLJ). So I would suggest that you will need something to lower the 8v signal to below 5v.
Regards
Simon
PS. The datasheet can be found @ http://pdfserv.maxim-ic.com/en/ds/MAX220-MAX249.pdf