Start software, select COM, press 'START' 4. (verified by probing with a scope) So I tried an firmware-update: 1. I have the same issue: Sending SMS works, but I never receiver anything on the RX-line. By the way, suggests that there is a different debug port UART on the SIM900 and that this should be used for debugging and firmware updates.Īre you sure the firmware updater will work with the regular UART? About the UART， it is the right one。 I have confirm it with our supplier. In 115200, the firmware updater keeps sending decimal 22, and never receives a respond. In 19200 baud, the firmware updater keeps sending decimal 255 and never receives a response. I have now tried to run the updater in 19200 bauds, and listened in. OK, as I said, I didn't use the PWRKEY button, I used a jumper to connect pin 1 directly to GND. By the way, when push the PWRKEY button PIN1 and PIN2 of SIM900 are connect together. In this way, you don't need to pushing button all the time. Jimbo.we wrote:You can try to solder a wire to PIN1 of SIM900, and wire it to GND. Are you sure the firmware updater will work with the regular UART?Īttachments (15.74 KiB) Downloaded 249 times. By the way, suggests that there is a different debug port UART on the SIM900 and that this should be used for debugging and firmware updates. This afternoon I will probably try to connect the logic analyzer again to see exactly what the update tool sends over the wire. I did not use the button for the upgrade process.

I did actually connect PIN1 directly to GND and nothing else, as I described. Is there a different sequence of steps I should try? Can I ask which baud rate you use for firmware updates? Edited to attach a photo of the setup the TX and RX pins are only connected to my USB/TTL thing at the top left. Also in every case, the Netlight and Status LEDs light up like they would normally do, and Netlight does off after 10-15 seconds. Every time, no reaction from the firmware updater. Connect GND to pin 1 (PWRKEY), hold it there.Pres START in the updater, wait for 'Please power up the target' message.Every time I get the message 'Please power up the target', at which point nothing happens. While PWRKEY is still connected to GND, press START in the updater.

Connect GND to pin 1 (PWRKEY) on SIM900 with jumper wire, hold it there (at this point the board starts powering up normally, netlight and status light up as if I had just preseed the button).

Separate jumper wire that I use to connect GND directly to pin 1 on the SIM900 chip.įor the various baud rates up to 115200, I do this:.

I assume these go through the level shifter.

TX and RX directly to the USB/TTL cable from the GPRS_TX and GPRS_RX pins.GPRS Shield power provided from a Seeduino.This worked, I received the SMS, but again (as usual) I never receive a response from the GPRS Shield to AT commands. To test that my UART cable works, I used a terminal emulator to send an SMS. I connected the GPRS Shield to a USB to TTL UART cable that I obtained here. Thank you so much for your patience! I am still trying to upgrade firmware. After you connect the wire(here PWRKEY(PIN 1) of SIM900 should be connected to GND during the whole process), first press START of Simcom - sim900 Customer flash loader V1.01 (before this process the module is power down, completely disconnect from any power) then power up the module( connect to power ). GPRS_TX and GPRS_RX should disconnect from other purpose. Jimbo.we wrote:You can use the use the GPRS_TX and GPRS_RX pins with UartSBee or equal.

Simcom flash update tool v1 10