Using PICs as UARTs

[tumbleweed]

If you don't mind setting a unique ID in the UserID area when you initially program the chip (say 1 to 4 for example), then you could use this setting to identify which of the four uarts the chip is supposed to be and have the master use the General Call address feature of the I2C to assign a new address to the device at powerup. It could be as simple as sending a packet to the General Call address consisting of the ID number and the new address.

No additional lines required.

[Dave]

dhouston, Doensn't the pic have an A/D? With a couple of fixed 1% resistors you can have quite a few addresses...

[dhouston]

dhouston, Doensn't the pic have an A/D? With a couple of fixed 1% resistors you can have quite a few addresses...

Dave - I had thought of that but I am using the hardware EUSART and the hardware I2C so the only free pin is the MCLR pin which is input only - no ADC.

But, see my answers above - the availability of the ds30 Bootloader for the chips I'm planning to use solves my problem.

[dhouston]

If you don't mind setting a unique ID in the UserID area when you initially program the chip (say 1 to 4 for example), then you could use this setting to identify which of the four uarts the chip is supposed to be and have the master use the General Call address feature of the I2C to assign a new address to the device at powerup. It could be as simple as sending a packet to the General Call address consisting of the ID number and the new address.

I guess I did not explain my concerns clearly.

Microchip will preprogram chips when you order them. All four chips will be have identical firmware except for the I2C address which must relate to a physical port (S2-S5) which is, in turn, related to the physical location of each chip on the PCB.

The logistics of keeping 4 separate chips separate and then assembling them to the correct PCB location is what scares me. On another board, I have two sets of two identical chips (2x12F1822, 2x16F1823), that ID themselves upon startup by the state of one input which is grounded for one socket and tied high for the other - and these are DIP chips with sockets so it's not as critical that they be assembled correctly. I was trying to find a way to extend that to handle four identical chips.

However, the issue is now moot. The ds30 bootloader has been updated to support all three PICs I am using (12F1822, 16F1823, 12F1840) and it allows writing EEPROM so they can have the bootloader installed by Microchip and then be programmed over a serial link after assembly or even by the end user.