# BX310x cannot transfer binary data over BT SPP **URL:** \ **Category:** WiFi and Bluetooth Modules\ **Created:** [November 21, 2019, 4:48pm UTC](https://forum.sierrawireless.com/t/bx310x-cannot-transfer-binary-data-over-bt-spp/18417 "2019-11-21T16:48:42Z")\ **Posts on this page:** 3\ **Page:** 1
**Author:** ![vipul.vishnoi](https://avatars.discourse-cdn.com/v4/letter/v/85f322/32.png) [@vipul.vishnoi](https://forum.sierrawireless.com/u/vipul.vishnoi)\ **Post date:** [November 21, 2019, 4:48pm UTC](https://forum.sierrawireless.com/t/bx310x-cannot-transfer-binary-data-over-bt-spp/18417/1 "2019-11-21T16:48:42Z")
I am trying to send binary data over BT SPP and it seems like the chip can only do ASCII even when I am in data mode. The binary data I am trying to send is the MODBUS protocol. **Firmware version** : BX310x.2.6.3 **Communication** : UART, 115200, 8 data bits, No parity, 1 stop bit, hardware flow control enabled (AT&K3) **AT command sequence:** ``` AT+RST OK AT+SRBTSYSTEM? +SRBTSYSTEM: 2 OK AT+SRBTCPROFILES? +SRBTCPROFILES: 1 OK AT+SRBTSTATE? +SRBTSTATE=1,2 OK // After this, the remote device discovers the module and requests to open a SPP connection. Here are the notifications I get: +SRBTPAIR: “6c:00:6b:73:20:c0”, 1 +SRBTCFG: 1,0, “6c:00:6b:73:20:c0”,SPP,0 +SRSPPCNX:1,1,129 // Once I receive the +SRSPPCNX notification, I set the SPP connection to data mode: AT+SRSPPSTART=1 CONNECT ``` I don’t have a console log for the data bytes, but I have a logic analyzer that shows the data bytes being sent to the UART port of the BT module. I have attached a screenshot with timestamps ![BT%20UART%20port%20capture](https://us1.discourse-cdn.com/flex025/uploads/sierrawireless/original/2X/5/5bf7511d7b9037a0381806961360f196e4012a27.png) As for AT+SRSPPSND command, the reference manual states that it only supports ASCII. I need to be able to send the full unsigned 8-bit range of binary data 0-255. This isn’t possible unless we send individual digits encoded in ASCII. While this may be ok for newer applications that can parse ASCII, it will not be a drop-in replacement for existing applications that accept binary only. I think this limits the applications with this chip by a lot and a firmware fix for this should not be too difficult. Please advice ---
**Author:** ![cherokee](https://avatars.discourse-cdn.com/v4/letter/c/76d3ee/32.png) [@cherokee](https://forum.sierrawireless.com/u/cherokee)\ **Post date:** [November 26, 2019, 3:34am UTC](https://forum.sierrawireless.com/t/bx310x-cannot-transfer-binary-data-over-bt-spp/18417/2 "2019-11-26T03:34:50Z")
Hi @vipul.vishnoi, This is the limitation of the current module. Sierra is also aware of this issue. I think new firmware release will be updated soon to fix the issue. " ---
**Author:** ![g.riccardo](https://avatars.discourse-cdn.com/v4/letter/g/d6d6ee/32.png) [@g.riccardo](https://forum.sierrawireless.com/u/g.riccardo)\ **Post date:** [February 4, 2021, 2:06pm UTC](https://forum.sierrawireless.com/t/bx310x-cannot-transfer-binary-data-over-bt-spp/18417/3 "2021-02-04T14:06:34Z")
There is any news on this topic from sierra wireless company? I work with BX3105 and they are very happy ok for me and our application, but we work with SPP on BT and I need to send and receive many bytes of status and configuration of my system. I tryed to send from my pc to BX3105 module more bytes (over 700) and I receive all without problem. But when I need to send from BX3105 in SPP mode to My PC, I have the limit of 256/3 = 85 bytes. This because I need to format the AT command for send with this sintax: AT+SendCommand: ‘/’,‘2’,‘1’ just for send a value of 0x21 hexadecimal and so on. There is in the future 1 upgrade for send more than 256 byte **together** on SPP session sent command? Now I work with firmware version 2.7.3. The last available in this moment. Thank a lot for all suggestion and information.